Remove unnecessary checks in api.py

Remove existing check to ensure instance was running
when adding or removing security groups to/from an
instance.
Modified unit test accordingly
Fixes bug 1107721

Change-Id: If1148653edd96bd70b983c2fa89cd9973d80e48b
Merge "Remove unnecessary checks in api.py"
Merge remote-tracking branch 'm_src_repo/master' into build-temp