Use l3plugin property in neutron/db/l3_dvr_db.py module
Use l3plugin property in neutron/db/l3_dvr_db.py module

Class DVRResourceOperationHandler has got property called
l3plugin which returns directory.get_plugin(plugin_constants.L3)
so there is no need to use directory.get_plugin(plugin_constants.L3)
in other places in this class.

TrivialFix

Change-Id: I6cc0fb4cd5edb798569dabe8f9c8696020e79008

noironetworks/neutron,openstack/neutron,mahak/neutron,mahak/neutron,noironetworks/neutron,mahak/neutron,openstack/neutron,openstack/neutron