Fix race in 'BackgroundConsumer._thread_main'. (#8883)

See #7817.

Author: tseaver

packages/google-api-core/google/api_core/bidi.py

@@ -642,7 +642,7 @@ def _thread_main(self, ready):
                 # In the future, we could use `Condition.wait_for` if we drop
                 # Python 2.7.
                 with self._wake:
-                    if self._paused:
+                    while self._paused:
                         _LOGGER.debug("paused, waiting for waking.")
                         self._wake.wait()
                         _LOGGER.debug("woken.")