migrate: Fix cancelling state warning

We've been getting the warning:

migration_iteration_finish: Unknown ending state 2

on a cancel.

I think that's originally due to 39b9e179;  although
I've only seen the warning, I think that in some cases
that we could find the VM stays paused after a cancel where
it should restart.
Signed-off-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Message-Id: <20180719092257.12703-1-dgilbert@redhat.com>
Reviewed-by: NPeter Xu <peterx@redhat.com>
Reviewed-by: NJuan Quintela <quintela@redhat.com>
Signed-off-by: NDr. David Alan Gilbert <dgilbert@redhat.com>

migration/migration.c

@@ -2877,6 +2877,7 @@ static void migration_iteration_finish(MigrationState *s)
         /* Fallthrough */
     case MIGRATION_STATUS_FAILED:
     case MIGRATION_STATUS_CANCELLED:
+    case MIGRATION_STATUS_CANCELLING:
         if (s->vm_was_running) {
             vm_start();
         } else {