move cinder_config and glance_api_config changes from ceph to cinder and glance modules
refactor Ceph init.pp

 * extract ceph.conf handling into ceph::conf
 * rename ceph::deploy to ceph::mds (and leave it disabled)
 * move libnss handling to ceph::libnss class in params.pp
 * move ceph service definition to ceph::params
 * simplify role-dependent declarations and ordering rules
 * include ceph::cinder for cinder nodes, but don't include ceph classes
   by default for unrecognized node roles
 * install python-pushy instead of pushy in Debian-based systems
 * minor formatting fixes to calm down puppet-lint
refactor Ceph mon.pp

 * drop keyring file declarations, check for ceph-create-keys instead of
   running ceph-deploy gatherkeys to check for Ceph cluster quorum
 * move Ceph client ACLs definition to cinder.pp and glance.pp
 * extract c_pools subclass into a proper ceph::osd_pools class
 * parametrize Cinder and Glance pool names explicitly and separately
   instead of accessing them by indices in a list
 * drop the checks for $::glance_api_conf and $::cinder_conf