SecurityMiddleware and the three cache middlewares were not calling
super().__init__() during their initialization or calling the required
MiddlewareMixin._async_check() method.
This made the middlewares not properly present as coroutine and
confused the middleware chain when used in a fully async context.
Thanks Kordian Kowalski for the report.
Backport of 825ce75faec63ce81601e31152c757a9c28fed13 from master