Lazily create TaskMaster in 'rejester' program

This avoids extra redis connections in some specific cases, and
more importantly, tries harder to avoid a log call before calling
daemon and setting up logging in 'rejester run_worker'.
Avoid "no handlers found" message in tests

Specifically create a logging.NullHandler to run in cleanup code.
pytest_capturelog creates its own handler for the root logger, which
is good, but tears it down before fixture cleanup code runs.