Suppress meaningless opentsdb metrics connection warning

[timbeccue]

Set default OPENTSDB_PYTHON_METRICS_TEST_MODE=1 in banzai/__init__.py so users don't see this confusing error on every run:

ERROR: metric_wrappers: ConnectionError(MaxRetryError("HTTPConnectionPool(host='scheduler-dev.lco.gtn', port=80): Max retries exceeded with url: /api/version (Caused by NewConnectionError('<urllib3.connection.HTTPConnection object at 0x112013230>: Failed to establish a new connection: [Errno 8] nodename nor servname provided, or not known'))"))

[timbeccue]

The current solution only sets OPENTSDB_PYTHON_METRICS_TEST_MODE if we're not in prod because using any value at all evaluated to True. I made an update to opentsdb-python-metrics so in version 0.3.0, setting that variable to '0' or 'false' correctly sets test mode to off.

We could make this solution cleaner by having banzai's production deployment explicitly configure OPENTSDB_PYTHON_METRICS_TEST_MODE to be 'false', then also safely use a default of 'true' for all other cases.

However, the ocs ingester needs to be updated to use opentsdb-python-metrics 0.3.0 first, and then banzai needs to specify that version of the ingester before we can access this change.

[cmccully]

Add a change log message and bump the last digit of the version. Otherwise looks good.