Add some progress logging to the performance benchmark script

The [performance benchmark script|https://github.com/jbosstm/performance/blob/master/narayana/scripts/hudson/bm.sh] was seen to time out on a recent pull request with no indication of why the job was not making progress.

Whenever the [benchmark run script|https://github.com/jbosstm/performance/blob/master/narayana/scripts/hudson/benchmark.sh] starts a new run it should report which test iteration it is running, then we will at least be able to tell how much progress was made before Jenkins times out the build.