spec: declare we provide an existing python-cpopen

Currently, vdsm-python-cpopen claims to provide python-cpopen = 4.13.1,
which is not true, as no such version exists. Worse, if may cause issue
in a future occasion of someone trying to replace vdsm-python-cpopen
with python-cpopen-1.2.17.

Change-Id: I424b934811a30d95ba3349fbf3d9b65f0dc8c4b8
Signed-off-by: Dan Kenigsberg <danken@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/21058
Reviewed-by: Antoni Segura Puimedon <asegurap@redhat.com>
Reviewed-by: David Caro <dcaroest@redhat.com>
Reviewed-by: Yaniv Bronhaim <ybronhei@redhat.com>