Plugin/DB additions for version 2 of LBaaS API

Added alembic migrations, models, db methods and plugin methods.
Added DEFERRED status for entities not linked to a load balancer.

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

Change-Id: Iaec2c2315ae54418b341eb31e6b3ff53b02ca9d7
Co-authored-by: Brandon Logan <brandon.logan@rackspace.com>
Co-authored-by: Vijayendra Bhamidipati <vbhamidipati@paypal.com>
Co-authored-by: Craig Tracey <Craig.Tracey@gmail.com>
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>
Implement Jinja templates for haproxy config

Added templates dir
Added haproxy v1.4 template
Added template tests
Added jinja_cfg for new haproxy jinja templating

Partially-implements: blueprint lbaas-api-and-objmodel-improvement
Partially-implements: blueprint lbaas-refactor-haproxy-namespace-driver-to-new-driver-interface

Change-Id: Iad3a7be0146e1148b29edee56233aa3196c982dc
Co-authored-by: Phillip Toohill <phillip.toohill@rackspace.com>
Co-authored-by: Dustin Lundquist <dustin@null-ptr.net>
Agentless haproxy driver methods used by managers

Implemented driver methods that create network namespace and haproxy process.
Added tests.

Change-Id: Ia2abaedf9ef46110ce5b2d4e033c0f79ae68e089
Implemented lbaas managers

Change-Id: I08557ccf2936f8029ea60d07c285bb692d4c0b54