sms/dtap: Add log messages to analyse SMS message loss

Incoming DTAP messages from MS are discarded during silent calls,
which leads to the repeated delivery of SMS since the ACKs are not
being processed.

This patch adds some log messages that have been helpful to track
this down.

Sponsored-by: On-Waves ehf
diff --git a/openbsc/src/libmsc/osmo_msc.c b/openbsc/src/libmsc/osmo_msc.c
index 31b72b9..f3badb7 100644
--- a/openbsc/src/libmsc/osmo_msc.c
+++ b/openbsc/src/libmsc/osmo_msc.c
@@ -59,6 +59,8 @@
 		return BSC_API_CONN_POL_ACCEPT;
 	if (trans_has_conn(conn))
 		return BSC_API_CONN_POL_ACCEPT;
+
+	LOGP(DRR, LOGL_INFO, "MSC Complete L3: Rejecting connection.\n");
 	return BSC_API_CONN_POL_REJECT;
 }
 
@@ -71,11 +73,13 @@
 			     uint8_t rr_cause, uint8_t chosen_channel,
 			     uint8_t encr_alg_id, uint8_t speec)
 {
+	LOGP(DRR, LOGL_DEBUG, "MSC assign complete (do nothing).\n");
 }
 
 static void msc_assign_fail(struct gsm_subscriber_connection *conn,
 			    uint8_t cause, uint8_t *rr_cause)
 {
+	LOGP(DRR, LOGL_DEBUG, "MSC assign failure (do nothing).\n");
 }
 
 static void msc_classmark_chg(struct gsm_subscriber_connection *conn,