Switch to testenv:functional
Switch to testenv:functional

This brings our tox.ini files inline with other OpenStack projects.

Change-Id: I074ffc326c5e659afb5e66d16475a92035a4cb7d
Depends-On: I376e51824c46f9b5eb4a4cff01aaa176632087dd
Signed-off-by: Paul Belanger <e7139c8e6c4ea75cc1c287ce081b2dc0f3ab39ec@redhat.com>

openstack/ansible-role-diskimage-builder