Avoid shutting off a paused VM instance

Currently, "Shut Off Instance" option is enabled even on a paused VM instance
which results in an error that says "Error: Unable to shut off instance".
With this commit, we are removing the option to shut off a paused VM instance.

Change-Id: I95da413a398632d9300333a4dbaf028b7c6a6f68
Closes-Bug: #1372620
Merge "Avoid shutting off a paused VM instance"