Filter verbose oauth2client log messages

"Attempting refresh to obtain initial access_token" (https://github.com/googleapis/oauth2client/blob/50d20532a748f18e53f7d24ccbe6647132c979a9/oauth2client/transport.py#L157) is a verbose log message that confuse users.

oauth2client is deprecated and owners are not planning to fix this. We can mask it with a log filter (https://docs.python.org/2/library/logging.html#filter-objects) here (https://github.com/apache/beam/blob/a1cb61ab63acff2c3d93f166d59f4789d45ecc11/sdks/python/apache_beam/runners/worker/logger.py#L178)