intermittent failure in test_ping

[anschweitzer]

Failed in CI, here.

Error output:

 >           assert (pings_from_scada + pings_from_atn) >= exp_pings_nominal, err_str
E           AssertionError: pings_from_atn: 2
E             messages_from_atn: 12
E             pings_from_scada: 2
E             messages_from_scada: 20
E             exp_pings_nominal: 5.0
E             
E           assert (2 + 2) >= 5.0

tests/test_proactor/test_proactor_comm.py:924: AssertionError

This looks like an ill-controlled test; it appears more messages were sent during the wait than expected, so less pings were necessary.

[anschweitzer]

Also here in gridworks-proactor