core: LiveMigrateDiskCommand - audit log on failure

Since LiveMigrateDiskCommand is an internal command,
canDoAction error messages aren't displayed to the user.
Hence, invoke an AuditLog message on canDoAction failure.

Change-Id: Ie326395fe9d610f578829c9c5b8847097dfc7b27
Bug-Url: https://bugzilla.redhat.com/968203
Signed-off-by: Daniel Erez <derez@redhat.com>