pipewire-jack: use jack_client_close() to free client in error path

The client needs to be cleaned up properly, otherwise references
to its storage may remain, which can later result in use-after-frees.
For example, the via the various embedded `spa_hook`s in it.

See #2394

pipewire-jack/src/pipewire-jack.c

@@ -3436,7 +3436,7 @@ server_failed:
 exit_unlock:
 	pw_thread_loop_unlock(client->context.loop);
 exit:
-	free(client);
+	jack_client_close((jack_client_t *) client);
 	return NULL;
 disabled:
 	if (status)