[Samba] aio settings for samba 4.3

[Russell R Poyner]

Thanks for all the zfs tuning tips. The point is a good one.

I was concerned that zfs performance might be limiting, and posted tests 
run against a ufs formatted ram disk for that reason. The tests with the 
ram disk are slightly faster than the zfs backed tests, but still slower 
than tests run with samba on linux using xfs on a single hard disk.

Russ Poyner