Use the previous commit on returning success from each task execution
function, and implement handling of errors in the main loop. Add a
script with which this is visible using Custom_Commands.
Add some basic unit tests to verify that Iperf/Ping work. Harmonize the
logging by only print in the "main" iperf/ping function, to avoid that
if we test with multiple UEs, the output intermixes. Also, do one common
mkdir before starting multiple pings/iperfs. Finally, harmonize the
paths so that Iperf and Ping log their files in the same place.