message: Added GroupType property in HybridWorkerGroup
diff: "credential": {
  "$ref": "#/definitions/RunAsCredentialAssociationProperty",
  "description": "Sets the credential of a worker group."
  + },
  + "groupType": {
  + "type": "string",
  + "description": "Type of the HybridWorkerGroup.",
  + "enum": [
  + "User",
  + "System"
  + ],
  + "x-ms-enum": {
  + "name": "GroupTypeEnum",
  + "modelAsString": true
  + }
  }
  },
  "description": "Definition of hybrid runbook worker group."
  