vdsClient: hibernate now sends required hiberVolHandle

- vdsClient did not pass hiberVolHandle, causing it to fail any attempt
to hibernate
- BindigsXMLRPC defaulted required parameter to None

Change-Id: Id703a349bac7d75d3acb7e124392ac05d25e2869
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=802446
Signed-off-by: Martin Polednik <mpoledni@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/18280
Reviewed-by: Dan Kenigsberg <danken@redhat.com>