Example override yaml file is added to indicate how to
override the manifest for configure an additional externally
managed Ceph Cinder backend.
In ceph.conf, either "mon_host" or "mon host" can be used for
the same parameter. In order not to force the user to use it one
way or the other, "mon_host" is removed from default setting.
Change-Id: I179567d77196ab2fb82d7a78e3a08efb966ed68c
085a0dd1a9