core: avoid removing a vm also when migratingTo

The fix simplifies the check and states what states we CAN delete the VM
, otherwise fail canDoAction

Change-Id: I6d97fbe84a81a3a4704ed1d80d9b52da752c108a
Bug-Url: https://bugzilla.redhat.com/947965
Signed-off-by: Roy Golan <rgolan@redhat.com>