getWriter() has already been called for this response error while send unauthorized request to Artifactory

Steps to reproduce:

1. Create virtual Maven repository "libs-snapshot" that aggregate local Maven repository "libs-snapshot-local":
2. Disable anonymous permissions on the local repository
3. Deploy some jar file to the local repository, add a folder to the path
4. Fetch the folder using cURL: like the following:

   $ curl  http://localhost:8081/artifactory/libs-snapshot/org/jfrog/test/multi1/3.7-SNAPSHOT/

In artifactory.log you will see getWriter() error.

In case you run the cURL with credentials, the output will be an HTML file that describes the folder content.