Adds the run for 8
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Return current txg as an int

Just like in the linux specific version, return it as an int so that we
can easily do maths with it, which is probably the more common use.
Also print out the txgs/second
Removes all the TXG watching

Two reasons:
1) It has become impossible to do with reasonable accuracy on a default
installation of 0.6.3, and asking people to change a kernel module
variable to run the default tests seems a bit steep.
2) The numbers meaning is not as trivial to deduce as the speed in mib/sec
so just throwing it at people is not the best idea.
First swing at a log reader

The log files that come off these tests can be parsed to extract data
after the run.
Get the logfile as an argument