Expose /var/run/ceph

Expose /var/run/ceph

Useful for softwares that do data collection/monitoring like collectd.
They can connect to the socket and then retrieve information.

Even though the sockets are exposed now, I'm keeping the docker exec to
check the socket, this will allow newer version of ceph-ansible to work
with older versions.

Closes: https://bugzilla.redhat.com/show_bug.cgi?id=1563280
Signed-off-by: Sébastien Han <seb@redhat.com>