core: better illegal VM status message

Enriched the "The VM status is illegal" message to contain
also the localized version of the status which is illegal.

Change-Id: Iea6840e555aeb0c7a33a3b90e72fef23433e2be1
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1000068
Signed-off-by: Tomas Jelinek <tjelinek@redhat.com>