mgcp_conn: rename field s/rate_ctr_group/ctrg/g

This makes all lines operating on rate groups way shorter. The "ctrg"
naming is already used in tons of places in osmocom code.

Change-Id: I745eddbf66e7d811bb73c8ae9bb54ea93073c71b
diff --git a/src/libosmo-mgcp/mgcp_stat.c b/src/libosmo-mgcp/mgcp_stat.c
index e679882..d134526 100644
--- a/src/libosmo-mgcp/mgcp_stat.c
+++ b/src/libosmo-mgcp/mgcp_stat.c
@@ -39,7 +39,7 @@
 void calc_loss(struct mgcp_conn_rtp *conn, uint32_t *expected, int *loss)
 {
 	struct mgcp_rtp_state *state = &conn->state;
-	struct rate_ctr *packets_rx = rate_ctr_group_get_ctr(conn->rate_ctr_group, RTP_PACKETS_RX_CTR);
+	struct rate_ctr *packets_rx = rate_ctr_group_get_ctr(conn->ctrg, RTP_PACKETS_RX_CTR);
 
 	*expected = state->stats.cycles + state->stats.max_seq;
 	*expected = *expected - state->stats.base_seq + 1;
@@ -80,10 +80,10 @@
 	int ploss;
 	int nchars;
 
-	struct rate_ctr *packets_rx = rate_ctr_group_get_ctr(conn->rate_ctr_group, RTP_PACKETS_RX_CTR);
-	struct rate_ctr *octets_rx = rate_ctr_group_get_ctr(conn->rate_ctr_group, RTP_OCTETS_RX_CTR);
-	struct rate_ctr *packets_tx = rate_ctr_group_get_ctr(conn->rate_ctr_group, RTP_PACKETS_TX_CTR);
-	struct rate_ctr *octets_tx = rate_ctr_group_get_ctr(conn->rate_ctr_group, RTP_OCTETS_TX_CTR);
+	struct rate_ctr *packets_rx = rate_ctr_group_get_ctr(conn->ctrg, RTP_PACKETS_RX_CTR);
+	struct rate_ctr *octets_rx = rate_ctr_group_get_ctr(conn->ctrg, RTP_OCTETS_RX_CTR);
+	struct rate_ctr *packets_tx = rate_ctr_group_get_ctr(conn->ctrg, RTP_PACKETS_TX_CTR);
+	struct rate_ctr *octets_tx = rate_ctr_group_get_ctr(conn->ctrg, RTP_OCTETS_TX_CTR);
 
 	calc_loss(conn, &expected, &ploss);
 	jitter = calc_jitter(&conn->state);