explicitly free codecs in mgcp_rtp_conn_cleanup()

There are allocated bits in conn->end.codecs[], free them.

This is not fixing a memleak, since mgcp_rtp_conn_cleanup() is currently only
called from mgcp_conn_free(), which soon after frees the conn; the conn serves
as talloc parent for the codec strings freed in this patch.

The rationale: it is better style to explicitly free them, to also guard
against future callers of mgcp_rtp_conn_cleanup() which might expect complete
cleanup.

Change-Id: Ic471107ce6e94d9ce582d887429c744ff93e3053
diff --git a/src/libosmo-mgcp/mgcp_conn.c b/src/libosmo-mgcp/mgcp_conn.c
index 772584b..60a1700 100644
--- a/src/libosmo-mgcp/mgcp_conn.c
+++ b/src/libosmo-mgcp/mgcp_conn.c
@@ -129,6 +129,7 @@
 		conn_osmux_disable(conn_rtp);
 	mgcp_free_rtp_port(&conn_rtp->end);
 	rate_ctr_group_free(conn_rtp->rate_ctr_group);
+	mgcp_codec_reset_all(conn_rtp);
 }
 
 void mgcp_conn_watchdog_cb(void *data)