vdsm-upgrade: fix xml format

Fixed illegal XML that affects upgrade from Engine.

Change-Id: I019bc35eaebd7c0b0424353f6c7e5699f3eb27b4
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=920671
Signed-off-by: Douglas Schilling Landgraf <dougsland@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/12990
Reviewed-by: Joey Boggs <jboggs@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>