vdsm.spec: Remove Obsoletes: python-cpopen

python-cpopen spec obsoletes vdsm-python-cpopen, so vdsm.spec don't
need to obsolete python-cpopen. Otherwise, it will generate an
infinity loop during the yum update between these packages.

Change-Id: If5523c3530cbac667ce5c7db4f78543f21778c54
Signed-off-by: Douglas Schilling Landgraf <dougsland@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/22113
Reviewed-by: Yaniv Bronhaim <ybronhei@redhat.com>
Tested-by: Yaniv Bronhaim <ybronhei@redhat.com>