packaging: ship systemd/ceph.tmpfiles.d in tarballs

packaging: ship systemd/ceph.tmpfiles.d in tarballs

Prior to this commit, the tarballs did not contain
any files under the top-level "systemd" directory. This caused problems
with RPM builds on Fedora and RHEL 7, because as of commit
aa88364f30e2d2f254ade185a83ba263b48e2a73, those RPMs depend on the
systemd/ceph.tmpfiles.d file.

(Longer-term we might want to improve the tarball generation code to be
less complex/manual.)

http://tracker.ceph.com/issues/11383 Refe: #11383

Reported-by: Greg Farnum <gfarnum@redhat.com>
Signed-off-by: Ken Dreyer <kdreyer@redhat.com>