JENKINS-50812. The DNS Multi-cast logic is rarely used in Jenkins, but it always tries to start DNS Multicast on startup. It slows down the startup and usually leads to errors since Jenkins instances have no such permissions on default setups.
Even after https://github.com/jenkinsci/jenkins/commit/031ccdf038b9589bd347acc94800d9f52d110023#diff-00764bfce077b2ca25f1d86e490a5e8a by Jesse Glick the issue is quite annoying, especially in test logic.
Since the functionality is not really used on the most of instances, I propose to disable it. It is formally a breaking change, so it requires a short JEP and discussion in the mailing list.