Base ML2 bulk support on the loaded drivers
Base ML2 bulk support on the loaded drivers

Changes the ML2 plugin bulk support flag to
be based on the bulk support of the underlying
drivers.

Closes-Bug: #1272490
Change-Id: I28281c9ecc1696b929c7e0125d02a37946948744

openstack/neutron-fwaas,gaolichuang/neutron-fwaas,citrix-openstack-build/neutron-fwaas,dougwig/x-neutron-fwaas,openstack/neutron-fwaas,gaolichuang/neutron-fwaas