Be more aggressive about killing TDS

[portante]

If this triggers, then we know that the TDS got far enough to daemonize itself but that it died or got stuck before it could report in. Shouldn't we at least look and see if it created a PID file that we can use to kill it if it's stuck? (This seems like a piece of utility code which pbench-tool-meister-stop could share.)

Originally posted by @webbnh in #2076 (comment)

[portante]

This will be partially addressed by PR #2181, but the shared code between pbench-tool-meister-stop and pbench-tool-meister-start will not be addressed with that PR.