core: When ActivateVDS fails, move VDS out of Unassigned status

If ActivateVDS command fails, in some rare scenarios the VDS will be
stuck on Unassigned status, locking any ability to remove/activate the
VDS. This patch will move failed VDS to Error status.

Change-Id: I776fb9fd0fe3292ad257c7bcfaf4ac8c89536869
Bug-Url: https://bugzilla.redhat.com/962180
Signed-off-by: lzelkha@redhat.com <lzelkha@redhat.com>