(QENG-803) Modify Gatling Perf tests to get load data from driver and master nodes

(QENG-803) Modify Gatling Perf tests to get load data from driver and master nodes

Basically, launching Gatling was previously taken care of by directly invoking the script. This wraps that up in a beaker test job in order to utilize beaker's performance gathering feature (install sysstat and produce data at the end of the run)
ok.  (that's really unfortunate that they are managing their artifacts that way, though.)