watchdog: fix timeout not running if polling returned early

Switch from running the loop with UV_RUN_ONCE to UV_RUN_DEFAULT, because
it's possible that the poll returns earlier than expected and thus the
timer is not run on a single interation.

The loop is not stopped either from the timer callback or from the async
handle's.

src/node_watchdog.cc

@@ -65,8 +65,9 @@ void Watchdog::Destroy() {
 void Watchdog::Run(void* arg) {
   Watchdog* wd = static_cast<Watchdog*>(arg);
 
-  // UV_RUN_ONCE so async_ or timer_ wakeup exits uv_run() call.
-  uv_run(wd->loop_, UV_RUN_ONCE);
+  // UV_RUN_DEFAULT the loop will be stopped either by the async or the
+  // timer handle.
+  uv_run(wd->loop_, UV_RUN_DEFAULT);
 
   // Loop ref count reaches zero when both handles are closed.
   // Close the timer handle on this side and let Destroy() close async_
@@ -75,11 +76,14 @@ void Watchdog::Run(void* arg) {
 
 
 void Watchdog::Async(uv_async_t* async) {
+  Watchdog* w = ContainerOf(&Watchdog::async_, async);
+  uv_stop(w->loop_);
 }
 
 
 void Watchdog::Timer(uv_timer_t* timer) {
   Watchdog* w = ContainerOf(&Watchdog::timer_, timer);
+  uv_stop(w->loop_);
   V8::TerminateExecution(w->env()->isolate());
 }