zbd: Ensure first I/O is write for random read/write to sequential zones

zbd: Ensure first I/O is write for random read/write to sequential zones

In case read is chosen for the first random I/O for sequential write
required zones, fio stops because no data can be read from the zones with
empty status. Enforce to write at the first I/O to make sure data to read
exists for the following read operations.

The unexpected fio stop symptom was observed with test case #30 of
t/zbd/test-zbd-support. When the test case was run repeatedly resetting
all zones with -r option, it often passes with too short run time.

Reviewed-by: Damien Le Moal <damien.lemoaal@wdc.com>
Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>