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: I2e85732585ec3fc0cd0ee124aea8c065a697a7f4
Merge "HA support for ceph-rest-api."