add LOG_RAN_CONN() to use the conn->fi->id for context

For each conn, set a default logging category, to distinguish categories for
BSSMAP and RANAP based conns.

LOG_RAN_CONN(): log with the conn's default category,

LOG_RAN_CONN_CAT(): log with a manually set category (mostly for keeping
previous DMM logging on the same category).

In some places, replace LOGP() using manual context with LOG_RAN_CONN(), and
remove the manual context info, now provided by the conn->fi->id.

This is loosely related to inter-BSC and inter-MSC handover: to speed up
refactoring, I want to avoid the need for manual logging context and just use
this LOG_RAN_CONN().

Change-Id: I0a7809840428b1e028df6eb683bc5ffcc8df474a
diff --git a/src/libmsc/ran_conn.c b/src/libmsc/ran_conn.c
index d6349eb..714907f 100644
--- a/src/libmsc/ran_conn.c
+++ b/src/libmsc/ran_conn.c
@@ -651,6 +651,18 @@
 		.fi = fi,
 	};
 
+	switch (via_ran) {
+	case OSMO_RAT_GERAN_A:
+		conn->log_subsys = DBSSAP;
+		break;
+	case OSMO_RAT_UTRAN_IU:
+		conn->log_subsys = DRANAP;
+		break;
+	default:
+		conn->log_subsys = DMSC;
+		break;
+	}
+
 	fi->priv = conn;
 	llist_add_tail(&conn->entry, &network->ran_conns);
 	return conn;