Better solution to exit_code problem without breaking zombie reaping

Fix exit codes. Get reaper to work again. Wait for --run commands properly.
Beef up zombie_maker, so it becomes its own process group leader, closes stdin, stdout, stderr
Correct zombie reaping tests
Run more tests in the foreground (not as docker run -d) so they will less sensitive to timing issues
Bug fixes: close the sigs channel, finish --run commands before we start tailing the log files of the primary service (which isn't even running yet).