Update supported Fedora releases
Update supported Fedora releases

Fedora 27 has now hit EOL [1] while Fedora 29 has been released [2].

[1] https://fedoramagazine.org/fedora-27-end-of-life/
[2] https://fedoramagazine.org/announcing-fedora-29/

Change-Id: I12e287e36f01581f1c7145545ab05be527ed15c6

dtroyer/devstack,openstack-dev/devstack,openstack-dev/devstack,nawawi/openstack,dtroyer/devstack,nawawi/openstack