await asyncio.ensure_future

[manics]

All other calls to asyncio.ensure_future were either awaited or in one case saved to a member variable, so I've awaited the remaining calls in spawner.py but I'm not sure how to thoroughly test this. I didn't notice any problems when testing this on a small local Z2JH deployment.

$ git grep -n -A2 ensure_future -- kubespawner/spawner.py

kubespawner/spawner.py:2805:            await asyncio.ensure_future(previous_reflector.stop())
kubespawner/spawner.py-2806-
kubespawner/spawner.py-2807-        # wait for first load
--
kubespawner/spawner.py:2867:        futures = [asyncio.ensure_future(task) for task in tasks]
kubespawner/spawner.py-2868-        try:
kubespawner/spawner.py-2869-            await asyncio.gather(*futures)
--
kubespawner/spawner.py:2886:        self._start_future = asyncio.ensure_future(self._start())
kubespawner/spawner.py-2887-        return self._start_future
kubespawner/spawner.py-2888-
--
kubespawner/spawner.py:3089:        start_futures = [asyncio.ensure_future(task) for task in start_tasks]
kubespawner/spawner.py-3090-        try:
kubespawner/spawner.py-3091-            await asyncio.gather(*start_futures)
--
kubespawner/spawner.py:3257:                await asyncio.ensure_future(self._start_watching_pods(replace=True))
kubespawner/spawner.py-3258-            raise
kubespawner/spawner.py-3259-
--
kubespawner/spawner.py:3382:            await asyncio.ensure_future(self._start_watching_pods(replace=True))
kubespawner/spawner.py-3383-            raise
kubespawner/spawner.py-3384-

Related to #858