Re-instate --append-terse

Re-instate --append-terse

This wasn't well documented, but ensure that we don't people's
setup. The new way of doing multiple formats is to add them
to the output format. Which means that this:

fio --append-terse --output-format=normal

is now equivalent to

fio --output-format=normal,terse

Please use the latter.

Signed-off-by: Jens Axboe <axboe@fb.com>