[PATCH] Add 'norandommap' option

[PATCH] Add 'norandommap' option

With this option given, fio will not keep track of what parts of a file
has been read/written or not. So for random io, we may read/write a block
a block more than once (or not at all). Thus this option conflicts with
doing write verification.

This is a first step for doing truly randomly sized blocks of io.

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