Set keystonemiddleware and routes.middleware to log on WARN level

Thanks to I49a82c5b3446784d254ca558f51b6c3e5c2028eb, we can augment
oslo's set of default log levels with project specific ones.

Add keystonemiddleware as warn level since its verbose and nova isn't
trying to debug keystonemiddleware.

Add routes.middleware since this generates 3 log entries per API request
and doesn't help make debugging easier.

Change-Id: I4b762eea922fe358ed2d0ac409b3caecced6ec96
Merge "Set keystonemiddleware and routes.middleware to log on WARN level"