Fix grpc-gateway after grpc 1.18 upgrade (#501)
Fix grpc-gateway after grpc 1.18 upgrade (#501)


open-telemetry/opentelemetry-collector-contrib,open-telemetry/opentelemetry-collector,open-telemetry/opentelemetry-collector-contrib,open-telemetry/opentelemetry-collector,census-instrumentation/opencensus-service,open-telemetry/opentelemetry-collector,census-instrumentation/opencensus-service