Augment oslo's default log levels with nova specific ones.

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: Ib5164a22c5cbfa4f9d881b97bb1f623cd4d2f3f3
Merge "Augment oslo's default log levels with nova specific ones."