staging: lustre: fid: perform sanity checks before commiting

When fid fetches a new range from the server, it commits
to it (*output = *out) *before* performing sanity checks.
This looks backwards.
Don't commit to a value until it has been found to be sane.

Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>