GRPC Health Service hang detection

[guvenc]

Current GRPC healthcheck can not detect the hang of the worker thread in dpservice.
One idea would be to introduce a timeout in the below mentioned part of the GRPC handling code and if the timeout
happens, it would set its GRPC health state to NOT_SERVING.

Possibly effected code snippet.

while (cq_->Next(&tag, &ok) && ok) {
call = static_cast<BaseCall*>(tag);
while (call->HandleRpc() == CallState::AWAIT_MSG) {
// wait for response from worker
};
}