ceph.spec.in: include SUSE in _with_systemd

ceph.spec.in: include SUSE in _with_systemd

The master specfile newly defines a _with_systemd variable that should be true
for the set of distros that are using systemd. Since this set of distros
includes SUSE/openSUSE (at least for the more recent versions where ceph is
supported), this commit sets _with_systemdto true on SUSE/openSUSE.

http://tracker.ceph.com/issues/11610 Fixes: #11610

Signed-off-by: Nathan Cutler <ncutler@suse.cz>
(cherry picked from commit 61303656faa913880008e6a6a1725d2fd7002c1f)