No relevant message when stop a stopped VM

When user tries to stop a stopped VM, there is no need to stop it again,
and We need return it's vm_state.

Fixes bug 1181934

Change-Id: I71772dfcead440cb49b6ccdbb4e1a891475bb75e
(cherry picked from commit 62ca3783ce4fcc0b03e96936972abc83b54c772f)
Merge "No relevant message when stop a stopped VM" into stable/grizzly