CLI: log spam with warning about deprecated tls_context being used #364
Description
When using nighthawk_client, a warning-level log line [1] will always appear about nighthawk.client.CommandLineOptions.tls_context being used -- even while it's not actively being set as a configuration argument.
The warning should only emerge when it's being used actively configured.
[1] sample
[2020-06-16 20:51:43.610][79803][warning][misc] Deprecated field: type nighthawk.client.CommandLineOptions Using deprecated option 'nighthawk.client.CommandLineOptions.tls_context' from file options.proto. This configuration will be removed from Envoy soon.
Please see https://www.envoyproxy.io/docs/envoy/latest/version_history/version_history for details. If continued use of this field is absolutely necessary, see https://www.envoyproxy.io/docs/envoy/latest/configuration/operations/runtime#using-runtime-overrides-for-deprecated-features for how to apply a temporary and highly discouraged override.