Fix boot once option

The boot once options seems to have gotten broken since it originally
went in.  We need to wait until the second time restore_boot_devices()
gets called before restoring the standard boot order and removing itself
from the reset list.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
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Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>