Fix the broken PYTHONPATH

@builddir@/vdsm is a non-exsiting path

Change-Id: I438936a7eb98206426a15aa0a751a22060b9c895
Signed-off-by: Shu Ming <shuming@linux.vnet.ibm.com>
Reviewed-on: http://gerrit.ovirt.org/12509
Reviewed-by: Zhou Zheng Sheng <zhshzhou@linux.vnet.ibm.com>
Tested-by: Zhou Zheng Sheng <zhshzhou@linux.vnet.ibm.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>