Logging: systest teardown flakes with 404. #8676

______________________ TestLogging.test_log_root_handler _______________________
self = <test_system.TestLogging testMethod=test_log_root_handler>
    def tearDown(self):
        retry = RetryErrors((NotFound, TooManyRequests, RetryError), max_tries=9)
        for doomed in self.to_delete:
            try:
>               retry(doomed.delete)()
tests/system/test_system.py:111:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
../test_utils/test_utils/retry.py:108: in wrapped_function
    return to_wrap(*args, **kwargs)
google/cloud/logging/logger.py:223: in delete
    client.logging_api.logger_delete(self.project, self.name)
google/cloud/logging/_gapic.py:139: in logger_delete
    self._gapic_api.delete_log(path)
google/cloud/logging_v2/gapic/logging_service_v2_client.py:326: in delete_log
    request, retry=retry, timeout=timeout, metadata=metadata
../api_core/google/api_core/gapic_v1/method.py:143: in __call__
    return wrapped_func(*args, **kwargs)
../api_core/google/api_core/retry.py:273: in retry_wrapped_func
    on_error=on_error,
../api_core/google/api_core/retry.py:182: in retry_target
    return target()
../api_core/google/api_core/timeout.py:214: in func_with_timeout
    return func(*args, **kwargs)
../api_core/google/api_core/grpc_helpers.py:59: in error_remapped_callable
    six.raise_from(exceptions.from_grpc_error(exc), exc)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
value = NotFound(u'Log handler_root-1563211829508 does not exist',)
from_value = <_Rendezvous of RPC that terminated with:
	status = StatusCode.NOT_FOUND
	deta...pc_message":"Log handler_root-1563211829508 does not exist","grpc_status":5}"
>
    def raise_from(value, from_value):
>       raise value
E       NotFound: 404 Log handler_root-1563211829508 does not exist
.nox/system-2-7/lib/python2.7/site-packages/six.py:737: NotFound