Merge branch 'fix-dnssec-slave' into 'master'

Resign should also take place if ISPC Master is not the Nameserver.

We do only trigger a rewrite of the zonefile by touching server log so no need to chank against existance of a file.
Thanks to Tom Albers who pointed me to this issue by providing an excellent bug report!
Also removed some garbage

Probably this should even go into next 3.1 patch as it really can break DNSSEC when the nameserver is on a slave. Not talking about slave zones or replication but talking about a nameserver not running on ISPC Masterserver
Weird nobody noticed this yet... Thanks and Credits to @tom who noticed this

This fix has been successfully tested on a singleserver as well as toms Server where the issue occured.

See merge request !603