remove CEPH_ARGS from Nova and Cinder

Now that Nova and Cinder consistently pass --id option when executing rbd and
ceph commands, it's no longer necessary to set CEPH_ARGS environment variable
in the init scripts for Nova and Cinder services.

Change-Id: I29134942b1e7d5e2a276aecc00a9c5747cfa5a38
Closes-Bug: #1324954