changes in configfile.py.

1.) remove suffix space from '# VDSM backup '. This way we maintain backward comp
with libvirt_configure.sh

2.) on ovirt node wrap calls to rename with ovirt node unpersist and persist.
these calls use the new node namespace being ovirt.node.utils.fs.Config.

Change-Id: I76aced9da7a68eefdb60b82907bc83d224e449f5
Signed-off-by: Mooli Tayer <mtayer@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/28463
Reviewed-by: Douglas Schilling Landgraf <dougsland@redhat.com>
Reviewed-by: Yaniv Bronhaim <ybronhei@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>