Removes os-instance-usage-audit-log from the V3 API

The extension pre-dates ceilometer and equivalent
functionality is now much better managed using
ceilometer. So we're removing this before the V3 API
is officially released.

Partially implements blueprint v3-api-remove-extensions

Change-Id: I9b7892346a4ad7c54a903cfcbcb97156dfc8c734
Merge "Removes os-instance-usage-audit-log from the V3 API"