delete has no more data after the key (#53886)

Summary:
The tcpstore delete key implementation inadvertendly set "moreData" when sending the key when it was in fact the last message.

Thank you, PetrochukM, for the reproducing example which was instrumental in developing the fix (and is the blueprint for the test case).

Fixes #53872

Pull Request resolved: #53886

Reviewed By: jbschlosser

Differential Revision: D27011846

Pulled By: H-Huang

fbshipit-source-id: 5c460d1e4d095a8bc267bf63613b556856ced3e8

torch/lib/c10d/TCPStore.cpp

@@ -511,7 +511,7 @@ int64_t TCPStore::add(const std::string& key, int64_t value) {
 bool TCPStore::deleteKey(const std::string& key) {
   std::string regKey = regularPrefix_ + key;
   tcputil::sendValue<QueryType>(storeSocket_, QueryType::DELETE_KEY);
-  tcputil::sendString(storeSocket_, regKey, true);
+  tcputil::sendString(storeSocket_, regKey);
   auto numDeleted = tcputil::recvValue<int64_t>(storeSocket_);
   return (numDeleted == 1);
 }