Longrunning should use the service's YAML config, not longrunning's.

[lukesneeringer]

The client google.gapic.longrunning is passed certain information; this should include the client_config, which should take precedence over the values in operations_client_config.json.

Currently, the retry_params in the latter file seem to take precedence, which effectively cuts off API-level configuration for LRO operations.