I can't use windows instances in GCE because of launching agent problem. Please help me to debug/resolve the issue.

Steps to reproduce: 

1. Create windows instance in GCE
2. Login to the instance by RDP and add user tester with Administrator role
3. Login to the instance by RDP as tester
4. Install java8, cygwin with openssh, configure openssh (see how to here: https://docs.oracle.com/cd/E24628_01/install.121/e22624/preinstall_req_cygwin_ssh.htm#EMBSC281)
5. Check you are able to connect by ssh with tester user and its password
6. Create private/public rsa keypair (using ssh-keygen), put public key to the /home/tester/.ssh/authorized_keys file
7. Copy generated private key to your computer to ~/key.txt
8. Check you are able to connect to the instance with private key without password:
   ssh -i ~/key.txt tester@<ip_address>
9. Stop the instance and create an image from the instance
10. Goto http://<your_jenkins_address>/credentials/ page and add new credentials "SSH Username with private key", choose "enter directly" for private key and put generated private key here
11. Add new "Instance configuration" for created image on http://<your_jenkins_address>/configure page: set "Windows?" checkbox, set "Windows Username"=tester, set "Windows SSH Private Key Credentials" to credentials that were created on prev step, set Labels=windows-gce-test, set "Remote Location"=C:\jenkins
12. Run job with a label "windows-gce-test"

Expected: new GCE instance and jenkins slave are created, the slave is successfully connected and job is successfully ended

Actual: new GCE instance and jenkins slave are created, but slave can't connect

Slave output is the following:
INFO: Connecting to 35.233.217.99 on port 22, with timeout 10000.
Jan 10, 2019 4:42:07 AM null
INFO: Connected via SSH.
Jan 10, 2019 4:42:08 AM null
INFO: Copying slave.jar to: C:\
Jan 10, 2019 4:42:11 AM null
INFO: Verifying: java -fullversion
openjdk full version "1.8.0_181-b02"
Jan 10, 2019 4:42:12 AM null
INFO: Launching Jenkins agent via plugin SSH: java -jar C:\slave.jar
Jan 10, 2019 4:42:12 AM null
WARNING: Error: Exception: java.io.EOFException: unexpected stream termination

Jenkins log:
Connected via SSH.
Jan 10, 2019 5:04:02 AM INFO com.google.jenkins.plugins.computeengine.ComputeEngineCloud log
Copying slave.jar to: C:\
Jan 10, 2019 5:04:03 AM INFO com.google.jenkins.plugins.computeengine.ComputeEngineCloud log
Verifying: java -fullversion
Jan 10, 2019 5:04:03 AM INFO com.google.jenkins.plugins.computeengine.ComputeEngineCloud log
Launching Jenkins agent via plugin SSH: java -jar C:\slave.jar
Jan 10, 2019 5:04:03 AM WARNING com.google.jenkins.plugins.computeengine.ComputeEngineCloud log
Error:
java.io.EOFException: unexpected stream termination
at hudson.remoting.ChannelBuilder.negotiate(ChannelBuilder.java:408)
at hudson.remoting.ChannelBuilder.build(ChannelBuilder.java:353)
at hudson.slaves.SlaveComputer.setChannel(SlaveComputer.java:415)
at com.google.jenkins.plugins.computeengine.ComputeEngineWindowsLauncher.launch(ComputeEngineWindowsLauncher.java:128)
at com.google.jenkins.plugins.computeengine.ComputeEngineComputerLauncher.launch(ComputeEngineComputerLauncher.java:127)
at hudson.slaves.SlaveComputer$1.call(SlaveComputer.java:288)
at jenkins.util.ContextResettingExecutorService$2.call(ContextResettingExecutorService.java:46)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)

Jan 10, 2019 5:04:03 AM WARNING com.google.jenkins.plugins.computeengine.ComputeEngineCloud$1 call
Exception waiting for node zulu-win2016-tests-gce-enn0eu to connect
java.io.IOException: Agent failed to connect, even though the launcher didn't report it. See the log output for details.
at hudson.slaves.SlaveComputer$1.call(SlaveComputer.java:312)
Caused: java.util.concurrent.ExecutionException
at java.util.concurrent.FutureTask.report(FutureTask.java:122)
at java.util.concurrent.FutureTask.get(FutureTask.java:192)
at com.google.jenkins.plugins.computeengine.ComputeEngineCloud$1.call(ComputeEngineCloud.java:171)
at com.google.jenkins.plugins.computeengine.ComputeEngineCloud$1.call(ComputeEngineCloud.java:161)
at jenkins.util.ContextResettingExecutorService$2.call(ContextResettingExecutorService.java:46)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)

I'm not sure that GCE uses "Remote Location" for windows slaves (because the log says "INFO: Copying slave.jar to: C:\"). Could it be a cause of problem?

I'm unable to create GCE node because of JENKINS-55380 but tried to create permanent aget node and agent starts normally for it, I used the following parameters:
Permanent Agent
Remote root directory=.
Launch method=Launch agent agents via SSH
Credentails=<created_credentials_with_private_key>

Node log:
[01/10/19 05:14:27] [SSH] Checking java version of ./jdk/bin/java
Couldn't figure out the Java version of ./jdk/bin/java
bash: ./jdk/bin/java: No such file or directory

[01/10/19 05:14:27] [SSH] Checking java version of java
[01/10/19 05:14:27] [SSH] java -version returned 1.8.0_181.
[01/10/19 05:14:27] [SSH] Starting sftp client.
[01/10/19 05:14:28] [SSH] Copying latest remoting.jar...
[01/10/19 05:14:30] [SSH] Copied 762,466 bytes.
Expanded the channel window size to 4MB
[01/10/19 05:14:30] [SSH] Starting agent process: cd "." && java -jar remoting.jar -workDir .
Jan 10, 2019 1:14:30 PM org.jenkinsci.remoting.engine.WorkDirManager initializeWorkDir
INFO: Using .\remoting as a remoting work directory
Both error and output logs will be printed to .\remoting
<===[JENKINS REMOTING CAPACITY]===>channel started
Remoting version: 3.17
This is a Windows agent
NOTE: Relative remote path resolved to: C:\cygwin64\home\tester\.
Agent successfully connected and online