Rollback NLog4j to version 2.1.19, version 2.1.21 introduced some deps that  are not available.
Rollback NLog4j to version 2.1.19, version 2.1.21 introduced some deps that 
are not available.

git-svn-id: 5c3b06693d750a6aefbf1081b6b7d57c0165fdb2@370419 13f79535-47bb-0310-9956-ffa450edef68

apache/directory-project