[PATCH] Fix a bunch of bugs

[PATCH] Fix a bunch of bugs

- engines/fio-engine-libaio.o needs to link against -laio and fio need not
  anymore. This caused funky crashes with libaio io engine.

- Fix a few bugs in the libaio engine.

- Only do sync/cleanup in do_io() if we exit without error.

- ->io_ops may be NULL in reap_threads(), if the job exited.

- Allocate io engine, don't reuse the dlopen() object.

- Overlapping sprintf() in init_disk_util().

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