In the git plugin, when multiple repository URLs are configured (note: two remotes, not MultiSCM), polling fails to properly detect changes.

Steps to reproduce:

1. Create a job with two git repository URLs (note: two remotes, not MultiSCM). Ensure you name give the second one a different remote name. For example:

   origin -> git://github.com/blt04/jenkins-test1.git
   upstream -> git://github.com/blt04/jenkins-test2.git
   

2. Enable SCM polling (every minute works great)
3. Configure branch: "origin/master"
4. Run the job
5. Reconfigure job to use branch: "upstream/master"
6. Wait for polling to occur
7. Check polling log

Expected results:
Polling finds changes, triggers a build.

Actual results:
Polling does not find changes. Log looks similar to:

Using strategy: Default
[poll] Last Built Revision: Revision e377a52eaf5a0bf8b8bd6c175b2de0628d88226f (origin/master)
 > git -c core.askpass=true ls-remote -h git://github.com/blt04/jenkins-test master # timeout=10
[poll] Latest remote head revision is: e377a52eaf5a0bf8b8bd6c175b2de0628d88226f
Done. Took 0.27 sec
No changes