HTEX worker watchdog does not start workers

[rjmello]

Describe the bug
The HTEX Manager.worker_watchdog method creates a worker process object when a worker fails, but does not start the process.

To Reproduce

1. Run a function that kills the worker

@python_app
def kill_worker():
    import sys
    sys.exit(2)

2. Observe that no new worker process starts.

Expected behavior
The worker watchdog should recognize that the worker is dead and start a new process.

Environment

• Parsl version: 2023.11.20