Don't give pool slow warning if it is the donation pool.

main.c

@@ -3954,7 +3954,7 @@ static bool pool_active(struct pool *pool, bool pinging)
 	} else {
 		applog(LOG_DEBUG, "FAILED to retrieve work from pool %u %s",
 		       pool->pool_no, pool->rpc_url);
-		if (!pinging)
+		if (!pinging && pool != &donationpool)
 			applog(LOG_WARNING, "Pool %u slow/down or URL or credentials invalid", pool->pool_no);
 	}