build-rpms.sh: copy "*.patch" from topdir into SOURCES

This allows patches to be applied when building the RPMs; the addition
of the ceph patch to disable /etc/init.d/ceph from autostarting Ceph
daemons leads to the desire for a .patch file, conditionally applied
by the .spec.  See the Ceph sources.

Signed-off-by: Dan Mick <dan.mick@inktank.com>