Fix dispatcher crash on gevent LoopExit exceptions

Fix dispatcher crash on gevent LoopExit exceptions
Handle gevent LoopExit exceptions gracefully to prevent dispatcher
crashes. Add exception handling in main loop and lock_machines() call,
with loop exit counter (max 10) to prevent infinite restarts. Isolate
child processes using start_new_session=True so job supervisors
continue running independently if dispatcher encounters exceptions.

Signed-off-by: deepssin <deepssin@redhat.com>