this change also fix the EnvironmentFile specified in rbdmap.service.
without this change EnvironmentFile in rbdmap.service is always
/etc/sysconfig/ceph even on debian derived distros. after this change,
this variable is /etc/default/ceph in rbdmap.service shipped by the deb
packages.
Signed-off-by: Kefu Chai <kchai@redhat.com>
