Tests for extension, db and plugin for LBaaS V2

Adding needed driver interface changes for tests.
Adding LoggingNoop driver needed changes for tests.
Adding extension, plugin, and db unit tests.

Partially-implements: blueprint lbaas-api-and-objmodel-improvement

Change-Id: I1f7762bf3c9484b8bf46ce32ab78574aa081324b
Co-authored-by: Brandon Logan <brandon.logan@rackspace.com>
Co-authored-by: Phillip Toohill <phillip.toohill@rackspace.com>
Co-authored-by: Doug Wiegley <dougw@a10networks.com>