libbsc/libmsc: convert old osmo counter into rate_ctrgs

rate counters support the export to statsd and can have a delta value.

Change-Id: Ie749cebd53a0bb618d0e23d375885712078bf8dd
diff --git a/openbsc/src/libbsc/gsm_04_08_utils.c b/openbsc/src/libbsc/gsm_04_08_utils.c
index 635665a..d4eca4a 100644
--- a/openbsc/src/libbsc/gsm_04_08_utils.c
+++ b/openbsc/src/libbsc/gsm_04_08_utils.c
@@ -304,7 +304,7 @@
 		subscr = conn->subscr;
 	}
 
-	osmo_counter_inc(bts->network->stats.paging.completed);
+	rate_ctr_inc(&bts->network->ratectrs->ctr[MSC_CTR_PAGING_COMPLETED]);
 
 	/* Stop paging on the bts we received the paging response */
 	paging_request_stop(conn->bts, subscr, conn, msg);