ceph.spec.in: require redhat-lsb-core

We need this for /lib/lsb/init-functions.

Fixes: #8028
Signed-off-by: Sage Weil <sage@inktank.com>
Merge pull request #1634 from ceph/wip-8028

rpm: add redhat-lsb dependency

Reviewed-by: Alfredo Deza <alfredo.deza@inktank.com>