oslib/linux-blkzoned: Allow reset zone before file set up

oslib/linux-blkzoned: Allow reset zone before file set up

To reset zones before file set up completion, modify the helper function
blkzoned_reset_wp() to work even when fio_file struct does not have valid
file descriptor yet. If the file descriptor is not available, open and
close the reset target file within the function. Otherwise use the
available descriptor to avoid file open/close overhead.

Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Reviewed-by: Dmitry Fomichev <dmitry.fomichev@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>