vdsm.spec: vdsm-python requires zombiereaper

vdsm/utils.py requires vdsm--python-zombiereaper

Change-Id: Idc51e4be421f98975c970926c507e226f868a9a1
Signed-off-by: Douglas Schilling Landgraf <dougsland@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/23168
Reviewed-by: Dan Kenigsberg <danken@redhat.com>