Resolved server and instance status redundancy

Instance and server resource's _check_active() methods were
stripping off an extra '(STATUS)' string from the status.
This change moves the code of consistently handling status
to the nova client in heat. So, both the resources need not
perform any exra stuff to determine the status.

Change-Id: Ib527c001a2cdae90de1545ccdd56ad722c724d07