[MEDIUM] fix broken redispatch option

Since the connection queueing was introduced, the "redispatch"
option could not cover the cases where a connection has been
refused by the server after having been marked "in progress".
The fix consists in doing a redispatch in the delayed connection
handling code.

Problem reported by Konrad Rzentarzewski.

src/backend.c

@@ -522,9 +522,6 @@ int srv_retryable_connect(struct session *t)
 		}
 		/* ensure that we have enough retries left */
 		if (srv_count_retry_down(t, conn_err)) {
-			/* let's try to offer this slot to anybody */
-			if (may_dequeue_tasks(t->srv, t->proxy))
-				task_wakeup(&rq, t->srv->queue_mgt);
 			return 1;
 		}
 	} while (t->srv == NULL || t->conn_retries > 0 || !(t->proxy->options & PR_O_REDISP));

src/proto_http.c

@@ -1454,6 +1454,30 @@ int process_srv(struct session *t)
 			if (srv_count_retry_down(t, conn_err))
 				return 1;
 
+			if (t->srv && t->conn_retries == 0 && t->proxy->options & PR_O_REDISP) {
+				/* We're on our last chance, and the REDISP option was specified.
+				 * We will ignore cookie and force to balance or use the dispatcher.
+				 */
+				/* let's try to offer this slot to anybody */
+				if (may_dequeue_tasks(t->srv, t->proxy))
+					task_wakeup(&rq, t->srv->queue_mgt);
+
+				if (t->srv)
+					t->srv->failed_conns++;
+				t->proxy->failed_conns++;
+
+				t->flags &= ~(SN_DIRECT | SN_ASSIGNED | SN_ADDR_SET);
+				t->srv = NULL; /* it's left to the dispatcher to choose a server */
+				if ((t->flags & SN_CK_MASK) == SN_CK_VALID) {
+					t->flags &= ~SN_CK_MASK;
+					t->flags |= SN_CK_DOWN;
+				}
+
+				/* first, get a connection */
+				if (srv_redispatch_connect(t))
+					return t->srv_state != SV_STIDLE;
+			}
+
 			do {
 				/* Now we will try to either reconnect to the same server or
 				 * connect to another server. If the connection gets queued