Fix wrong CoroutineMock and Redis pool behaviour.
Fix wrong CoroutineMock and Redis pool behaviour.

Original Redis pool have magick method __await__ to create exclusive
connection. CoroutineMock sees this method and thinks that RedisPool
instance is awaitable and tries to await it.
To avoit this behavior we are using constructor with Mock.side_effect
instead of Mock.return_value.

joanvila/aioredlock