a_reset: Rename SIGTRAN connection to BSSMAP MSC assocation in log messages

Explanation from Harald:
There are plenty of things that can happen above the bare SCTP/M3UA
connection which can happen, such as SCCP or MTP level routing
problems.

The fact that a MSC responds to a BSSMAP reset tells us that all of
the underlying SS7 transport network is operational and the MSC
responds to us.

Go draw an IP analogy: Saying "SIGTAN connection up" here is like
saying "Ethernet link up" when you get an ICMP response.

Change-Id: If9d37c94f2f2b6cffef97f445774766993f538db
diff --git a/src/osmo-bsc/a_reset.c b/src/osmo-bsc/a_reset.c
index 63273e9..f990e63 100644
--- a/src/osmo-bsc/a_reset.c
+++ b/src/osmo-bsc/a_reset.c
@@ -82,7 +82,7 @@
 	struct reset_ctx *reset_ctx = (struct reset_ctx *)fi->priv;
 	struct bsc_msc_data *msc = reset_ctx->priv;
 
-	LOGPFSML(fi, LOGL_NOTICE, "SIGTRAN connection down, reconnecting...\n");
+	LOGPFSML(fi, LOGL_NOTICE, "BSSMAP MSC assocation is down, reconnecting...\n");
 	if (prev_state != ST_DISC)
 		osmo_stat_item_dec(msc->msc_statg->items[MSC_STAT_MSC_LINKS_ACTIVE], 1);
 }
@@ -112,7 +112,7 @@
 	struct reset_ctx *reset_ctx = (struct reset_ctx *)fi->priv;
 	struct bsc_msc_data *msc = reset_ctx->priv;
 
-	LOGPFSML(fi, LOGL_NOTICE, "SIGTRAN connection succeeded.\n");
+	LOGPFSML(fi, LOGL_NOTICE, "BSSMAP MSC assocation is up.\n");
 	if (prev_state != ST_CONN)
 		osmo_stat_item_inc(msc->msc_statg->items[MSC_STAT_MSC_LINKS_ACTIVE], 1);
 }