Make sure io_u->buflen is aligned to the verify_interval

If you specify verify and bs_unaligned you can make fio blow up in interesting
ways.  This is because the verify code assumes that the buflens will be bs
aligned and therefore aligned to the verify_interval.  However this isn't the
case for bs_unaligned.  So to fix this make sure we are always aligned to
verify_interval.  This keeps us from reading off the end of our io buf, or worse
writing past the end of it and makes this fio job pass properly instead of
blowing up.  Thanks,

Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Init buflen for our dummy buffer

If we fail to verify our buffer we will allocate a dummy buf to fill in so we
have something to compare our bad file to.  Unfortunately we don't set the
buflen of the dummy buffer which means we will sometimes write well past the end
of our buffer and this make glibc complain loudly.  Thanks,

Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>