lib-http: client: Drop peer immediately if it has no more linked queu…

…es and it is not connected and not waiting for a backoff timeout.

It is currently unlikely to happen at this point, but it is better to make sure it is handled appropriately.
The pending shared HTTP client changes will make this a likely event.
This surfaced as a problem for the HTTP proxy.

src/lib-http/http-client-peer.c

@@ -298,6 +298,11 @@ http_client_peer_handle_requests_real(struct http_client_peer *peer)
 	/* disconnect pending connections if we're not linked to any queue
 	   anymore */
 	if (array_count(&peer->queues) == 0) {
+		if (array_count(&peer->conns) == 0 && peer->to_backoff == NULL) {
+			/* peer is completely unused and inactive; drop it immediately */
+			http_client_peer_drop(&peer);
+			return;
+		}
 		http_client_peer_debug(peer,
 			"Peer no longer used; will now cancel pending connections "
 			"(%u connections exist)", array_count(&peer->conns));