[Core] fix keepalive in grpc client #33986

The keepalive grpc arguments is applied on a channel object that not used, thus it's not affective on worker client. This PR fixed it.

src/ray/rpc/grpc_client.h

@@ -99,9 +99,7 @@ class GrpcClient {
  ClientCallManager &call_manager,
  bool use_tls = false)
  : client_call_manager_(call_manager), use_tls_(use_tls) {
- std::shared_ptr<grpc::Channel> channel =
- BuildChannel(address, port, CreateDefaultChannelArguments());
- channel_ = BuildChannel(address, port);
+ channel_ = BuildChannel(address, port, CreateDefaultChannelArguments());
  stub_ = GrpcService::NewStub(channel_);
  }