Adjust dns.go to new miekg/dns package and improve error handling.
Adjust dns.go to new miekg/dns package and improve error handling.

When hitting the 64kiB limit of DNS, the error message so far was
really misleading.

amorken/prometheus,yanghongkjxy/prometheus,PrFalken/prometheus,alileza/prometheus,Stackdriver/stackdriver-prometheus,keegancsmith/prometheus,GoogleCloudPlatform/prometheus,dsymonds/prometheus,keegancsmith/prometheus,slok/prometheus,Stackdriver/stackdriver-prometheus,alileza/prometheus,Gouthamve/prometheus,Colstuwjx/prometheus,JavierZunzunegui/prometheus,Gouthamve/prometheus,datajet-io/prometheus,yanghongkjxy/prometheus,kzittritsch/prometheus,amorken/prometheus,Colstuwjx/prometheus,GoogleCloudPlatform/prometheus,GoogleCloudPlatform/prometheus,Conorbro/prometheus,datajet-io/prometheus,tomwilkie/prometheus,amorken/prometheus,brancz/prometheus,slok/prometheus,Stackdriver/stackdriver-prometheus,kzittritsch/prometheus,yanghongkjxy/prometheus,GoogleCloudPlatform/prometheus,prometheus/prometheus,prometheus/prometheus,keegancsmith/prometheus,PrFalken/prometheus,AlekSi/prometheus,prometheus/prometheus,SaltedMan/prometheus-annotated,dsymonds/prometheus,brancz/prometheus,Conorbro/prometheus,keegancsmith/prometheus,gottwald/prometheus,GoogleCloudPlatform/prometheus,gottwald/prometheus,kangwoo/prometheus,prometheus/prometheus,SaltedMan/prometheus-annotated,keegancsmith/prometheus,datajet-io/prometheus,agaoglu/prometheus,slok/prometheus,tomwilkie/prometheus,slok/prometheus,agaoglu/prometheus,JavierZunzunegui/prometheus,Stackdriver/stackdriver-prometheus,dsymonds/prometheus,Conorbro/prometheus,prometheus/prometheus,brancz/prometheus,AlekSi/prometheus,tomwilkie/prometheus,kzittritsch/prometheus,PrFalken/prometheus,brancz/prometheus,kangwoo/prometheus,agaoglu/prometheus,AlekSi/prometheus,agaoglu/prometheus,alileza/prometheus,kzittritsch/prometheus,gottwald/prometheus,Colstuwjx/prometheus,yanghongkjxy/prometheus,dsymonds/prometheus,Colstuwjx/prometheus,alileza/prometheus,tomwilkie/prometheus,Gouthamve/prometheus,kangwoo/prometheus,kangwoo/prometheus,Gouthamve/prometheus,datajet-io/prometheus,SaltedMan/prometheus-annotated,JavierZunzunegui/prometheus,JavierZunzunegui/prometheus,Conorbro/prometheus,gottwald/prometheus,amorken/prometheus,PrFalken/prometheus,AlekSi/prometheus,alileza/prometheus,SaltedMan/prometheus-annotated