Can't set default LBAAS provider in neutron plugin

[eon]

With the move of the lbaas driver to svc_monitor it is not possible anymore to specify a default lbaas provider.

The default provider "opencontrail" is hardcoded in the plugin.

[OpenContrail Admin (ci-admin-f)]

Review in progress for https://review.opencontrail.org/15523
Submitter: Jean-Philippe Braun (<email address hidden>)

[OpenContrail Admin (ci-admin-f)]

Reviewed: https://review.opencontrail.org/15523
Committed: http://github.org/Juniper/contrail-neutron-plugin/commit/e3f30ba37f13f8d07682061eb852473e715c55b7
Submitter: Zuul
Branch: master

commit e3f30ba37f13f8d07682061eb852473e715c55b7
Author: Jean-Philippe Braun <email address hidden>
Date: Mon Nov 30 16:52:01 2015 +0100

Allow to configure the default loadbalancer provider

By using a dummy loadbalancer driver it is possible to declare a default
provider for opencontrail.

In neutron.conf set:
service_provider=LOADBALANCER:haproxy:neutron_plugin_contrail.plugins.opencontrail.loadbalancer.driver.OpencontrailLoadbalancerDummyDriver:default
Then the default provider will be haproxy.

If no service_provider is set the default provider will be opencontrail
(the default provider created by SVC monitor)

Closes-Bug: #1521625
Change-Id: I112700e04ba485f5f48855d553dc345bf4c5fe74