AIO tests: increase limits

tests/sys/aio/aio_kqueue_test.c
Instead of using a hard-coded queue depth, use
vfs.aio.max_aio_queue_per_proc

tests/sys/aio/lio_kqueue_test.c
The old, small limit on lio_listio's operation count was lifted by
change 324941. Raise the operation count as high as possible without
exceeding the process's operation limit.

MFC after: 3 weeks
Sponsored by: Spectra Logic Corp