Pin test-requirements to match OpenStack requirements
Pin test-requirements to match OpenStack requirements

A new release of flake8 is causing lint faiures. Our requirements
should match OpenStack requirements anyway.

This patch pins to the current master requirements from the
OpenStack requirements repository using global-requirements.

Change-Id: Ic536d34a93e0e68bcb929379313baa8c5bac9aca

openstack/openstack-ansible-repo_server,openstack/openstack-ansible-repo_server,os-cloud/openstack-ansible-repo_server,os-cloud/openstack-ansible-repo_server