hosting: check_httpname_follow must use domain name, not hostname
hosting: add o+x on apps dir
site/david-lx1: fixup vpn link to actually come up after reboot
dasz/nagios_host: validate name
site/hetz3: fixups for dasz vpn

bridge_bridgeprio is especially important to keep the main bridge
on the stable part of the network and not flap to some external
subnet.
site/hetz3: Add no-ip-redirects according to hetzner's network requirements.