glusterfs: update for new API

Apparently glusterfs just changes their API as they see fit. Add
a configure check for the newer version, which adds pre/post stat
variables in a few random spots.

This should fix compilation with v6.0 of the API.

Fixes: https://github.com/axboe/fio/issues/781
Signed-off-by: Jens Axboe <axboe@kernel.dk>
4 files changed