Make RHEL installs honor ceph_origin: distro

Make RHEL installs honor ceph_origin: distro

Installs on RHEL with ceph_origin set to distro previously would fail
because no packages would get installed, but all of the checks passed
fine. This adds support for ceph_origin: distro, simply installing the
packages using yum/dnf and assuming that the sysadmin has provided a
repository containing them.

This also supports the use case where Satellite or a similar local
mirror is in use, and the admin does not or cannot use the additional
repositories the role would otherwise add.