Revert "VPNaaS: Temporarily disable check_migration"
Revert "VPNaaS: Temporarily disable check_migration"

Re-enable check_migration in pep8 job to validate HEAD file is correct.

This reverts commit 3f7b8309074b215eafafcbbe29963c7aa76bcfe1.

Related-Bug: #1475804
Depends-On: Ie4d20f5119018ffdebe2929b961c5ddb314ed734
Change-Id: Ie66a87492edf2b41b1c1b98c1812e2621b4db96a

openstack/neutron-vpnaas,openstack/neutron-vpnaas