Make policy debug logging less verbose

Nova recently synced in the latest policy code, and the api logs are now
filled with "Rule %s will now be enforced." In the nova context this log
isn't very useful and gets triggered multiple times per API call, as a
single API call can consist of multiple extensions.

Change-Id: I085d8fe12e92401d294ace8cc58da425e46deda2
Merge "Make policy debug logging less verbose"