core: SDValidator - fix message for locked SD

StorageDomainValidator -> isDomainExistAndActive:
if the storage domain is not in status Active,
the following canDo message should be returned:
"The relevant Storage Domain's status is ${status}"

Change-Id: I329d974710faa0437fe657c7e650aebb39960960
Bug-Url: https://bugzilla.redhat.com/1060516
Signed-off-by: Daniel Erez <derez@redhat.com>