[cdc_stream] Automatically start service (#28)

Starts the streaming service if it's not up and running. This required
adding the ability to run a detached process. By default, all child
processes are killed when the parent process exits. Since detached
child processes don't run with a console, they need to create sub-
processes with CREATE_NO_WINDOW since otherwise a new console pops up,
e.g. for every ssh command.

Polls for 20 seconds while the service starts up. For this purpose,
a BackgroundServiceClient is added. This will be reused in a future CL
by a new stop-service command to exit the service.

Also adds --service-port as additional argument to start-service.

cdc_stream/background_service_impl.cc

@@ -30,8 +30,8 @@ void BackgroundServiceImpl::SetExitCallback(ExitCallback exit_callback) {
 }
 
 grpc::Status BackgroundServiceImpl::Exit(grpc::ServerContext* context,
-                                         const ExitRequest* request,
-                                         ExitResponse* response) {
+                                         const EmptyProto* request,
+                                         EmptyProto* response) {
   LOG_INFO("RPC:Exit");
   if (exit_callback_) {
     return ToGrpcStatus(exit_callback_());
@@ -40,7 +40,7 @@ grpc::Status BackgroundServiceImpl::Exit(grpc::ServerContext* context,
 }
 
 grpc::Status BackgroundServiceImpl::GetPid(grpc::ServerContext* context,
-                                           const GetPidRequest* request,
+                                           const EmptyProto* request,
                                            GetPidResponse* response) {
   LOG_INFO("RPC:GetPid");
   response->set_pid(static_cast<int32_t>(Util::GetPid()));