Clarify that the pre_load function in a subsection is only called if
the subsection is found; to handle a missing subsection you may
set values in the pre_load of the parent vmsd.
Signed-off-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: NJuan Quintela <quintela@redhat.com>
Signed-off-by: NJuan Quintela <quintela@redhat.com>