Fix libvirt's getSchedulerParameters call

Python 2.6 does not support the short {} syntax for sets.

Change-Id: Icb4ef21f8d56363511460667dac359bf7e8b36a7
Signed-off-by: Martin Sivak <msivak@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/28044
Reviewed-by: Adam Litke <alitke@redhat.com>
Tested-by: Adam Litke <alitke@redhat.com>