Ubuntu: make hard coded group names configurable in configurator.py

In the sanlock part of our configurator, it uses qemu,kvm as the group
names. In Ubuntu the group names may be different. This patch makes the
two group names configurable.

Change-Id: I5e0f2513b1d7770bedeacbeb293593a2da8fe8ec
Signed-off-by: Zhou Zheng Sheng <zhshzhou@linux.vnet.ibm.com>
Reviewed-on: http://gerrit.ovirt.org/21296
Reviewed-by: Dan Kenigsberg <danken@redhat.com>