scripts: install-deps: Enable the EPEL repo when running in OpenStack CI
scripts: install-deps: Enable the EPEL repo when running in OpenStack CI

The nodes in the OpenStack CI may already have the epel repo present
but it could be disabled by default. As such, try to enable it as
early as possible.

Change-Id: Ib06f5aaf7f577d101b5b87f8cd81441380e56783

openstack/bifrost,openstack/bifrost