Revert "Merge pull request #1143 from Zentyal/jag/rpcproxy-dns-validation"

This reverts commit 63caeee671e7273f33bd725ca75becdf6ce39849, reversing
changes made to f742d2ce2d0cd754b89dd672c13b66f1e43114b7.

Conflicts:
	main/core/ChangeLog
Merge pull request #1149 from Zentyal/jacalvo/fix-dns-regression

Revert "Merge pull request #1143 from Zentyal/jag/rpcproxy-dns-validatio...