Use utils.persist instead of importing ovirt-node Config

Change-Id: I2daf816c08b8272fcac7bf6b3dd4571dc0b7852b
Signed-off-by: Yeela Kaplan <ykaplan@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/34075
Reviewed-by: Yaniv Bronhaim <ybronhei@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>