MINOR: queue: add a pointer to the server and the proxy in the queue

A queue is specific to a server or a proxy, so we don't need to place
this distinction inside all pendconns, it can be in the queue itself.
This commit adds the relevant fields "px" and "sv" into the struct
queue, and initializes them accordingly.

include/haproxy/queue.h

@@ -109,11 +109,18 @@ static inline int queue_limit_offset(int offset)
 	return offset;
 }
 
-static inline void queue_init(struct queue *queue)
+/* initialize the queue <queue> for proxy <px> and server <sv>. A server's
+ * always has both a valid proxy and a valid server. A proxy's queue only
+ * has a valid proxy and NULL for the server queue. This is how they're
+ * distinguished during operations.
+ */
+static inline void queue_init(struct queue *queue, struct proxy *px, struct server *sv)
 {
 	queue->head = EB_ROOT;
 	queue->length = 0;
 	queue->idx = 0;
+	queue->px = px;
+	queue->sv = sv;
 	HA_SPIN_INIT(&queue->lock);
 }