bugfixes for Ceph refactoring

 * merge conf_new and conf_pull back into ceph::conf
 * merge osd_pools back into ceph::mon
 * ceph-deploy gatherkeys has to run on primary mon, too
 * declare ceph service in init.pp instead of params.pp
 * don't re-run ceph-deploy osd prepare if the OSD devices are already
   listed in /proc/mounts
 * move ceph::libnss to its own file, include it in init.pp