dyn TS: fix: properly run an lchan activation timeout

Actually schedule an activation timer for the activation part of a dyn TS
switchover. It needs to be restarted because the channel release procedure in
the first part of a switchover actually removes the activation timer.

Change-Id: Ibf50d13ba10298464a8b07e34716763161438990
diff --git a/openbsc/src/libbsc/abis_rsl.c b/openbsc/src/libbsc/abis_rsl.c
index 42281ba..edc28a7 100644
--- a/openbsc/src/libbsc/abis_rsl.c
+++ b/openbsc/src/libbsc/abis_rsl.c
@@ -2487,6 +2487,13 @@
 	lchan->dyn.rqd_ref = NULL;
 	lchan->dyn.rqd_ta = 0;
 
+	/* During switchover, we have received a release ack, which means that
+	 * the act_timer has been stopped. Start the timer again so we mark
+	 * this channel broken if the activation ack comes too late. */
+	lchan->act_timer.cb = lchan_act_tmr_cb;
+	lchan->act_timer.data = lchan;
+	osmo_timer_schedule(&lchan->act_timer, 4, 0);
+
 	rc = rsl_chan_activate_lchan(lchan, act_type, ho_ref);
 	if (rc) {
 		LOGP(DRSL, LOGL_ERROR,