When using ssh, return values are not properly sent back from the remote system, even if the command returns a non zero value, the build is marked as a SUCCESS. If however, you use 'execute shell script' and perform the same task by issuing a remote command using (ssh -t) the correct value is returned to Jenkins.

There was a discussion on this issue here :
http://jenkins.361315.n4.nabble.com/Correct-exit-code-for-build-failure-td3305095.html