Extending quota support for neutron LBaaS entities

Part of extending quota mechanism to support neutron
LBaaS entities.
Adding new test for testing the lbaas resources.
The test is skipped if network lbaas extension is not available

This is one of four changes related to the BP.
This one is for tempest project.
Another one is for neutron project
and another one is for python-neutronclient package
and another one for horizon/openstack-dashboard project.

See blueprint neutron-quota-extension for another three changes.

Change-Id: I3b2739c28ff8dfbc4271d6f5d14b0655b6f9e203
Implements: blueprint neutron-quota-extension
Merge "Extending quota support for neutron LBaaS entities"