TT#14008 fix duplicate mutex_destroy

Change-Id: I14625106c5f2458b6b2a053a9ad863bfe69496a5
Warned-by: coverity

daemon/call.c

@@ -3549,7 +3549,6 @@ void call_media_free(struct call_media **mdp) {
 	codec_handler_free(&md->t38_handler);
 	t38_gateway_put(&md->t38_gateway);
 	g_queue_clear_full(&md->sdp_attributes, free);
-	mutex_destroy(&md->dtmf_lock);
 	g_queue_clear_full(&md->dtmf_recv, dtmf_event_free);
 	g_queue_clear_full(&md->dtmf_send, dtmf_event_free);
 	mutex_destroy(&md->dtmf_lock);