fix memleak: actually free strings in mgcp_codec_reset_all()

The audio_name and subtype_name are allocated from talloc, so they need to be
freed before resetting the codec array. Use mgcp_codec_free() to ensure this.

Change-Id: I07f207dcb7ce66bbf3445a30af41e696677b384f
diff --git a/src/libosmo-mgcp/mgcp_codec.c b/src/libosmo-mgcp/mgcp_codec.c
index 30c185c..7f1a6d1 100644
--- a/src/libosmo-mgcp/mgcp_codec.c
+++ b/src/libosmo-mgcp/mgcp_codec.c
@@ -100,7 +100,9 @@
  *  \param[out] conn related rtp-connection. */
 void mgcp_codec_reset_all(struct mgcp_conn_rtp *conn)
 {
-	memset(conn->end.codecs, 0, sizeof(conn->end.codecs));
+	int i;
+	for (i = 0; i < conn->end.codecs_assigned; i++)
+		codec_free(&conn->end.codecs[i]);
 	conn->end.codecs_assigned = 0;
 	conn->end.codec = NULL;
 }