bsc_msc: Stop the re-connect timer in case the msc is lost

It was possible to cause a crash by enabling and disabling the
MSC connection. The enabling lead to scheduling a connection
and the second call was not stopping the timer.
diff --git a/openbsc/src/libbsc/bsc_msc.c b/openbsc/src/libbsc/bsc_msc.c
index ccb0f4b..c8cdce0 100644
--- a/openbsc/src/libbsc/bsc_msc.c
+++ b/openbsc/src/libbsc/bsc_msc.c
@@ -243,6 +243,7 @@
 {
 	osmo_wqueue_clear(&con->write_queue);
 	osmo_timer_del(&con->timeout_timer);
+	osmo_timer_del(&con->reconnect_timer);
 
 	if (con->write_queue.bfd.fd >= 0)
 		osmo_fd_unregister(&con->write_queue.bfd);