add missing stopped status BACKOFF

add missing stopped status BACKOFF and update function to be more reziliant to new statuses.
Update supervisord.py

opps
Remove reactor approach. Just process the event.
Add docstring

Conflicts:
	salt/modules/test.py
Pylint whitespace
Merge pull request #17315 from cachedout/minion_master_error

Remove reactor approach. Just process the event.
Merge pull request #17316 from steverweber/supervisord_state_backoff

supervisord - add missing stopped status BACKOFF
six whitelisting
six whitelisting
Merge branch 'develop' into with-pylint-pragmas