Default to not capturing log output in tests

Viewing log output while tests are still running can be useful for
debugging, but log output was previously always captured.  This
change ensures that log capture is off by default, but can still
be enabled by setting OS_LOG_CAPTURE=1 in the shell environment.

testr invocation is unchanged and will continue to capture logs by
default.

Change-Id: I9d0fb648541280cacfebb47f67f608378ae66ef3
LBaaS integration with service type framework

The patch makes the following changes:

* adds new attribute of the pool: provider, which is provider name
as it is written in configuration
* adds support for multiple plugin drivers for loadbalancer
* cleans up healthmonitor-related plugin driver API
Drivers should work with healthmonitor associations only
* adds ability to update provider attribute for the pool used
to reassociate pools with new providers in case their providers
were removed from configuration

implements blueprint lbaas-integration-with-service-types

DocImpact

Change-Id: I4295c9bcceb38e60f813d5596af48bd8194c1c9b
Refactoring for nicira plugin to support NVP DHCP/Metadata services

This initial patch is aimed at decoupling core plugin services from
DHCP and metadata services. The abstraction being introduced is
needed so that the code can support both models where dhcp and
metadata services are provided by external RPC agents or solely by
the server-side plugin.

Supports blueprint nvp-dhcp-metadata-services

Change-Id: I396ee7bbcbd866e4e9d4a79887e844b4f5ec3c9e
Merge "LBaaS integration with service type framework"
Merge "Default to not capturing log output in tests"
Merge "Refactoring for nicira plugin to support NVP DHCP/Metadata services"