revert RequestGetHandler

paddle/fluid/operators/distributed/request_handler_impl.cc

@@ -100,11 +100,6 @@ bool RequestGetHandler::Handle(const std::string& varname,
     }
   } else {
     if (varname != FETCH_BARRIER_MESSAGE && varname != COMPLETE_MESSAGE) {
-      PADDLE_THROW(
-          "async mode should not send FETCH_BARRIER_MESSAGE or "
-          "COMPLETE_MESSAGE");
-    }
-
       if (enable_dc_asgd_) {
         // NOTE: the format is determined by distributed_transpiler.py
         std::string param_bak_name =
@@ -120,6 +115,7 @@ bool RequestGetHandler::Handle(const std::string& varname,
       }
       *outvar = scope_->FindVar(varname);
     }
+  }
   return true;
 }