ceph.spec.: add epoch

This is done in fedora packaging.  Do it here too so that you can move
between upstream packages (from ceph.com) and fedora and other derivatives
will builds.

Backport: firefly, dumpling
Signed-off-by: Sage Weil <sage@redhat.com>
Merge pull request #2614 from ceph/wip-rpm-epoch

rpm: set epoch 1 to match fedora

Reviewed-by: Boris Ranto <branto@redhat.com>