mkcephfs: create /var/run/ceph (or wherever pid_file and admin_socket live)
mkcephfs: create /var/run/ceph (or wherever pid_file and admin_socket live)

Fixes: #1546
Signed-off-by: Sage Weil <6dd34506bbd5e58221bbb3e4732d97c91f02277b@newdream.net>

ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph