vdsm_config: move download certificate

DHCP servers might delay to deliver the ip address
and we can't download the engine certificate from
vdsm-config stage. This patch is moving the download
certificate from vdsm-config to vdsm-reg-setup.

Change-Id: Ia2c025eedd2be92b9418ddbe01efc02c913af2a7
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1065368
Signed-off-by: Alon Bar-Lev <alonbl@redhat.com>
Signed-off-by: Douglas Schilling Landgraf <dougsland@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/26718
Reviewed-by: Dan Kenigsberg <danken@redhat.com>