Bugfix wait on start event (#7013)

* Bugfix wait on start event

* Paulus sugestion

* Change handling with stop_track_task

* Add new unittests

* Update test_core.py

tests/test_core.py

@@ -901,7 +901,6 @@ def test_start_taking_too_long(loop, caplog):
              patch('homeassistant.core._async_create_timer') as mock_timer:
             yield from hass.async_start()
 
-        assert not hass._track_task
         assert hass.state == ha.CoreState.running
         assert len(mock_timer.mock_calls) == 1
         assert mock_timer.mock_calls[0][1][0] is hass
@@ -910,3 +909,19 @@ def test_start_taking_too_long(loop, caplog):
     finally:
         yield from hass.async_stop()
         assert hass.state == ha.CoreState.not_running
+
+
+@asyncio.coroutine
+def test_track_task_functions(loop):
+    """Test function to start/stop track task and initial state."""
+    hass = ha.HomeAssistant(loop=loop)
+    try:
+        assert hass._track_task
+
+        hass.async_stop_track_tasks()
+        assert not hass._track_task
+
+        hass.async_track_tasks()
+        assert hass._track_task
+    finally:
+        yield from hass.async_stop()