nat: Count the number of dropped SCCP and MGCP calls as well.

Count the number of dropped calls and lost SCCP connections
due the loss of a connection to the BSC...
diff --git a/openbsc/src/nat/bsc_mgcp_utils.c b/openbsc/src/nat/bsc_mgcp_utils.c
index 5d24acf..ef55f8a 100644
--- a/openbsc/src/nat/bsc_mgcp_utils.c
+++ b/openbsc/src/nat/bsc_mgcp_utils.c
@@ -546,13 +546,21 @@
 
 void bsc_mgcp_clear_endpoints_for(struct bsc_connection *bsc)
 {
+	struct rate_ctr *ctr = NULL;
 	int i;
+
+	if (bsc->cfg)
+		ctr = &bsc->cfg->stats.ctrg->ctr[BCFG_CTR_DROPPED_CALLS];
+
 	for (i = 1; i < bsc->nat->mgcp_cfg->number_endpoints; ++i) {
 		struct bsc_endpoint *bsc_endp = &bsc->nat->bsc_endpoints[i];
 
 		if (bsc_endp->bsc != bsc)
 			continue;
 
+		if (ctr)
+			rate_ctr_inc(ctr);
+
 		bsc_mgcp_free_endpoint(bsc->nat, i);
 		mgcp_free_endp(&bsc->nat->mgcp_cfg->endpoints[i]);
 	}