Update to fedora-27 for testing
Update to fedora-27 for testing

We (openstack-infra) are in the process of removing fedora-26 from our
testing infrastructure. Update testing to use fedora-27 nodes.

Change-Id: I0a293849140bd2929dbcdb31fa08573802e5c61c
Depends-On: https://review.openstack.org/547107/
Depends-On: I148b1c8e265b327d60d76f88c036b032af014930
Signed-off-by: Paul Belanger <e7139c8e6c4ea75cc1c287ce081b2dc0f3ab39ec@redhat.com>

openstack/barbican,openstack/barbican