message: enableHttpCorrelationHeaders property is added to the Diagnostic entity
diff: "backend": {
  "$ref": "#/definitions/PipelineDiagnosticSettings",
  "description": "Diagnostic settings for incoming/outcoming HTTP messages to the Backend"
  + },
  + "enableHttpCorrelationHeaders": {
  + "type": "boolean",
  + "description": "Whether to process Correlation Headers coming to Api Management Service. Only applicable to Application Insights diagnostics. Default is true."
  }
  },
  "required": [
  