Do not reference CephBase from CephExternal service
Do not reference CephBase from CephExternal service

We want CephExternal to work without referencing CephBase which
instead defines common settings for hosted Ceph deployments.

This change fixes a reference to CephBase which was mistakenly
introduced with fix for bug #1632285.

Change-Id: Id27e935f91ad76a6877b3aa7588f54d6140aa41f
Closes-Bug: #1635014
(cherry picked from commit ba66980aa3d1fd981363173803e926642dc66227)

trozet/opnfv-tht,trozet/opnfv-tht,trozet/opnfv-tht