Description of problem:

As per upstream doc: [1] http://docs.ceph.com/docs/master/rbd/rados-rbd-cmds/#create-a-block-device-user

To create a Ceph user, with ceph specify the auth get-or-create command, user name, monitor caps, and OSD caps:

ceph auth get-or-create client.{ID} mon 'profile rbd' osd 'profile {profile name} [pool={pool-name}][, profile ...]'

For example, to create a user ID named qemu with read-write access to the pool vms and read-only access to the pool images, execute the following:

ceph auth get-or-create client.qemu mon 'profile rbd' osd 'profile rbd pool=vms, profile rbd-read-only pool=images'

The output from the ceph auth get-or-create command will be the keyring for the specified user, which can be written to /etc/ceph/ceph.client.{ID}.keyring.


Additional info:
This simplified rbd key creation should also be updated in 

Installation Guides: Appendix D. Manually Installing Ceph Block Device