Report conflict when python-cpopen is installed

vdsm-python-cpopen-4.13.2 cannot be installed in parallel to
python-cpopen, because the latter the user should manually take care of
removing python-cpopen if installed.
This patch adds a conflict report when this scenario occurs.

Change-Id: I0bcdf60a696e9b203555c83bda2c7053db5c6bfe
Signed-off-by: Yaniv Bronhaim <ybronhei@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/23632
Reviewed-by: Dan Kenigsberg <danken@redhat.com>
Reviewed-by: Douglas Schilling Landgraf <dougsland@redhat.com>