Most domestic broadband routers offer the option to provide names for
addresses on the local network in a private zone served by the router's
builtin forwarder and visible only to clients on the local network.
Some of these routers incorrectly advertise that zone with a leading dot
(e.g. ".home") in their DHCP offers. Unfortunately, Unbound refuses to
start if the name of a forwarding zone has a leading dot. Fix the
common case by trimming a single leading dot from the domain name, but
don't try to fix more complex misconfigurations.

PR: 296305
MFC after: 1 week