Copy Multiple Ceph Conf files into Cinder Containers

Working with our own distribution, we encountered the necessity of integrating Openstack (using Cinder) with 2 different Ceph backends.

In order to facilitate this specific integration, it is desirable to be able to store more than one ceph.conf file in the openstack configurations directory and copy these files into the cinder_volume and cinder_backup containers, in the default directory.

We propose a method in which all desired Ceph conf files must be placed inside a new `cinder/ceph/` directory and specify their paths relative to this directory in a new variable `ceph_conf_files:`.

The rest of the already existing process of copying Ceph conf files into containers is adapted to use this variable in order to copy all declared conf files.