libroot: ensure that the launch_daemon doesn't wait for itself.

* The launch_daemon might indirectly call get_launch_daemon_port()
  which may cause a deadlock. Just fail in this case.

src/system/libroot/os/launch.cpp

@@ -16,9 +16,18 @@ static port_id sLaunchDaemonPort = -1;
 port_id
 BPrivate::get_launch_daemon_port()
 {
-	if (sLaunchDaemonPort < 0)
+	if (sLaunchDaemonPort < 0) {
 		sLaunchDaemonPort = find_port(B_LAUNCH_DAEMON_PORT_NAME);
 
+		port_info info;
+		if (get_port_info(sLaunchDaemonPort, &info) == B_OK
+			&& info.team == find_thread(NULL)) {
+			// Make sure that the launch_daemon doesn't wait on itself
+			sLaunchDaemonPort = -1;
+			return -1;
+		}
+	}
+
 	return sLaunchDaemonPort;
 }