let blipp turn off a measurement when BLiPP sub process finished executing it. Also reorder part of the code, so that arbiter will check if processes are ended and turn off corresponding measurements before it looks for new measurements
Merge branch 'master' of https://github.com/periscope-ps/blipp

start merging blipp after gec20. seems I have a diverged version created for iptable on a different machine (mzhang-debian)