Docs: Document SSH key exchange for Ceph client
Docs: Document SSH key exchange for Ceph client

The ceph_client role requires that the deployment host's
SSH key be added to the authorized_keys on all of your Ceph
monitors if you choose the default behavior and do not specify
ceph.conf contents in a variable file.

Change-Id: Ie1b25f6d981f0c15b4bee0a64a14322af6039d85

openstack/openstack-ansible,stackforge/os-ansible-deployment,BjoernT/openstack-ansible,weezer/openstack-ansible,yanyao/openstack-ansible,cfarquhar/openstack-ansible,os-cloud/os-ansible-deployment,major/openstack-ansible,bunchc/openstack-ansible,cloudnull/os-ansible-deployment,bunchc/openstack-ansible,major/os-ansible-deployment,weezer/openstack-ansible,yanyao/openstack-ansible,Logan2211/openstack-ansible,Logan2211/openstack-ansible,major/openstack-ansible,cfarquhar/openstack-ansible,mancdaz/openstack-ansible,robb-romans/openstack-ansible,os-cloud/os-ansible-deployment,major/os-ansible-deployment,stackforge/os-ansible-deployment,cloudnull/os-ansible-deployment,openstack/openstack-ansible,BjoernT/os-ansible-deployment,mancdaz/openstack-ansible,yanyao/newton,BjoernT/openstack-ansible,robb-romans/openstack-ansible,BjoernT/os-ansible-deployment,yanyao/newton,BjoernT/os-ansible-deployment