vyos-hostsd: T4270: do not resolve local router FQDN to 127.0.1.1

Clients using VyOS as their DNS server and trying to resolve the FQDN of the
router will receive 127.0.1.1 as answer.

set service dns forwarding allow-from '172.16.0.0/12'
set service dns forwarding listen-address '172.31.0.254'
set service dns forwarding negative-ttl '60'
set system domain-name 'vyos.net'
set system host-name 'R1'

Will return:

$ host R1.vyos.net 172.31.0.254
Using domain server:
Name: 172.31.0.254
Address: 172.31.0.254#53
Aliases:

R1.vyos.net has address 127.0.1.1

When it should rather return the real IP address assigned via DNS.

(cherry picked from commit 665ae5072911fbb1373c393d9b57212552957888)