Remove duplicate import of constants module
Remove duplicate import of constants module

.. and enable corresponding pylint check now the only offending instance
is fixed.

Change-Id: I35a12ace46c872446b8c87d0aacce45e94d71bae

citrix-openstack-build/neutron-vpnaas,openstack/neutron-vpnaas,dougwig/x-neutron-vpnaas,openstack/neutron-vpnaas