Correct and consistent passing of provided event loop

[saaj]

AbstractActor's initialiser accepts external loop but it doesn't use the parameter correctly.

self._loop = kwargs.get('loop', asyncio.get_event_loop())

Here default event loop is retrieved even if user provided loop keyword argument. It leads to exception when default event loop is not initialised.

self._loop is not passed to Future at self._run_complete. Also QueryMessage need not to instantiate a Future on its own. Actor class is better to create the Future and pass its self._loop into it.

As a use case, here's recommendation for testing asyncio code from one of the library's authors.