polish multi process warning info (#19961)

test=develop

paddle/fluid/imperative/nccl_context.cc

@@ -82,11 +82,18 @@ void NCCLParallelContext::SendNCCLID(const std::string &ep,
   if (inet_pton(AF_INET, host.c_str(), &serv_addr.sin_addr) <= 0)
     PADDLE_THROW("invalied address: %s", ep);
 
+  int try_times = 0;
   while (true) {
     if (connect(sock, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) < 0) {
       VLOG(0) << "worker: " << ep
-              << " is not ready, will retry after 3 seconds...";
+              << (try_times < 5 ? " is not ready, will retry after 3 seconds..."
+                                : " is not ready. Maybe that some process "
+                                  "is occupied the GPUs of this node now, "
+                                  "and you should kill those process manually. "
+                                  "Will retry after 3 seconds...");
+
       std::this_thread::sleep_for(std::chrono::seconds(3));
+      ++try_times;
       continue;
     }
     VLOG(3) << "sending the ncclUniqueId to " << ep;