Packet cleanup without locks

Prevents use of invalid mutexes during mosquitto_destroy.

Closes #1914. Thanks to Nikolay Raspopov.

lib/mosquitto.c

@@ -294,7 +294,7 @@ void mosquitto__destroy(struct mosquitto *mosq)
 
 	mosquitto_property_free_all(&mosq->connect_properties);
 
-	packet__cleanup_all(mosq);
+	packet__cleanup_all_no_locks(mosq);
 
 	packet__cleanup(&mosq->in_packet);
 	if(mosq->sockpairR != INVALID_SOCKET){

lib/packet_mosq.c

@@ -100,13 +100,10 @@ void packet__cleanup(struct mosquitto__packet *packet)
 }
 
 
-void packet__cleanup_all(struct mosquitto *mosq)
+void packet__cleanup_all_no_locks(struct mosquitto *mosq)
 {
 	struct mosquitto__packet *packet;
 
-	pthread_mutex_lock(&mosq->current_out_packet_mutex);
-	pthread_mutex_lock(&mosq->out_packet_mutex);
-
 	/* Out packet cleanup */
 	if(mosq->out_packet && !mosq->current_out_packet){
 		mosq->current_out_packet = mosq->out_packet;
@@ -125,6 +122,14 @@ void packet__cleanup_all(struct mosquitto *mosq)
 	}
 
 	packet__cleanup(&mosq->in_packet);
+}
+
+void packet__cleanup_all(struct mosquitto *mosq)
+{
+	pthread_mutex_lock(&mosq->current_out_packet_mutex);
+	pthread_mutex_lock(&mosq->out_packet_mutex);
+
+	packet__cleanup_all_no_locks(mosq);
 
 	pthread_mutex_unlock(&mosq->out_packet_mutex);
 	pthread_mutex_unlock(&mosq->current_out_packet_mutex);

lib/packet_mosq.h

@@ -22,6 +22,7 @@ Contributors:
 int packet__alloc(struct mosquitto__packet *packet);
 void packet__cleanup(struct mosquitto__packet *packet);
 void packet__cleanup_all(struct mosquitto *mosq);
+void packet__cleanup_all_no_locks(struct mosquitto *mosq);
 int packet__queue(struct mosquitto *mosq, struct mosquitto__packet *packet);
 
 int packet__check_oversize(struct mosquitto *mosq, uint32_t remaining_length);