mncc_sock: Call osmo_fd_unregister() before closing and changing bfd->fd

Change-Id: I90f840da4cc26c1d970c3f5d18d3185678a1dba9
diff --git a/src/libmsc/mncc_sock.c b/src/libmsc/mncc_sock.c
index 7c65546..9c75d2c 100644
--- a/src/libmsc/mncc_sock.c
+++ b/src/libmsc/mncc_sock.c
@@ -71,9 +71,9 @@
 
 	LOGP(DMNCC, LOGL_NOTICE, "MNCC Socket has LOST connection\n");
 
+	osmo_fd_unregister(bfd);
 	close(bfd->fd);
 	bfd->fd = -1;
-	osmo_fd_unregister(bfd);
 
 	/* re-enable the generation of ACCEPT for new connections */
 	osmo_fd_read_enable(&state->listen_bfd);