Revert "Allow hostnames for delegate resolvers"
Revert "Allow hostnames for delegate resolvers"

This reverts commit 5f01360602c5f87b85c3e2a82847d4ab8ce6ef0a.

vivint-smarthome/mesos-dns,njuettner/mesos-dns,denen99/mesos-dns,mesosphere/mesos-dns,sepiroth887/mesos-dns,alberts/mesos-dns,denen99/mesos-dns,mcoffin/mesos-dns,mesosphere/mesos-dns,alberts/mesos-dns,Riptawr/mesos-dns,njuettner/mesos-dns,sepiroth887/mesos-dns,saagie/mesos-dns,vivint-smarthome/mesos-dns,mcoffin/mesos-dns,Riptawr/mesos-dns