HA support for ceph-rest-api.

Closes-Bug: #1386450
Issue: Need to add HA support for ceph-rest-api
Fix: 1. configured and spawned  rest-api process on all
        configured openstack nodes
     2. backend HA port is configured to 5006 and front
        end HA port is configured to 5005
     3. unconfigure ceph-rest-api support added on all
        configured openstack nodes.

Test: 1. Verified ceph-rest-api comes on configured backend
         port 5006
      2. Verified HA proxy listening on front end client
         port 5005
      3. Stopped ceph-rest-api process on the first openstack
         node and verified all requests moves to other nodes
Changed done based on review comments.
      Renamed rest-api server to ceph rest-api server

Change-Id: I7b578f2f2f09e9b2e78b19d08ddbaf94bd448dc5
Merge "HA support for ceph-rest-api." into R1.10