vdsm-reg: move OK message to caller.

Due bz#890572 engine.py now calls setVdsConf() to write into vdsm_reg.conf.
However, setVdsConf() prints an 'OK' message used in the old bootstrap and
it's showing in oVirt TUI. This patch will move this OK message to the
caller.

Change-Id: Ifaea56ca3f9f9a4f5e60c684dae9ae1f17f63a1e
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=925967
Signed-off-by: Douglas Schilling Landgraf <dougsland@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/14393
Reviewed-by: Dan Kenigsberg <danken@redhat.com>