overcloud_reboot: Specify path to ceph config in case of customized ceph cluster name
overcloud_reboot: Specify path to ceph config in case of customized ceph cluster name

DCN Distributed Mutlibackend environment deploy multiple ceph cluster with specific
Ceph cluster name for each cluster (in different Tripleo stacks). Each cluster has
configuration file named as "<$cluster>.conf" stored in /etc/ceph/.
ceph client looks for config file in /etc/ceph/ceph.conf by default which does not
exist in env with customized Ceph cluster name and thus It must be specified with using
option "-c /etc/ceph/<$cluster>.conf"
I have not found an easy and not hacky way how to find what's the ceph cluster name
used on some specific ceph node. The solution implemented looks for ceph-mon process
and tries to parse out cluster name from command line (the option is --cluster
<$cluster_name>).
Eventually heat should have CephClusterName parameter for each Tripleo stack but
Infrared and overcloud_reboot playbook has no awarness of stacks.

Change-Id: Ic7b09cc333c524fc6594e617d172c4a81a34f3ca

redhat-openstack/infrared,redhat-openstack/infrared,redhat-openstack/infrared