WARNING: BREAKS CONFIG COMPATIBILITY!
This commit changes the configuration interface of the NIC router in a way that
may break systems that use the component without proper adjustment!
How to adjust:
At each occurrence of the 'dns_server_from' attribute in a NIC router
configuration replace the attribute name with 'dns_config_from'. The attribute
value remains unaltered.
DETAILED DESCRIPTION
The new attribute name 'dns_config_from' reflects that also other aspects of
the DNS configuration of the denominated domain are used by the DHCP server
that holds the attribute. This commit is a preparation for forwarding also the
domain name (DHCP option 15) with the mechanism behind the attribute.
Ref #4246