stream_srv: sctp: Log error cause of COMM_LOST event

RFC 6458 6.1.1:
"""
sac_error:  If the state was reached due to an error condition (e.g.,
SCTP_COMM_LOST), any relevant error information is available in
this field.  This corresponds to the protocol error codes defined
in [RFC4960].
"""
Change-Id: Ie48360d22ce1e35eefb1a305dde106948dfa80e8
---
M src/stream_srv.c
1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/src/stream_srv.c b/src/stream_srv.c
index cccb811..6c50a69 100644
--- a/src/stream_srv.c
+++ b/src/stream_srv.c
@@ -856,7 +856,8 @@
 				LOGPC(DLINP, LOGL_DEBUG, " UP\n");
 				break;
 			case SCTP_COMM_LOST:
-				LOGPC(DLINP, LOGL_DEBUG, " LOST\n");
+				LOGPC(DLINP, LOGL_DEBUG, " COMM_LOST (err: %s)\n",
+				      osmo_sctp_sn_error_str(notif->sn_assoc_change.sac_error));
 				/* Handle this like a regular disconnect */
 				return 0;
 			case SCTP_RESTART:

