[Samba] specify alternative port for samba internal dns server

[Ben Cohen]

I asked this question on serverfault
http://serverfault.com/questions/666972/possible-to-make-samba4s-internal-dns-server-listen-on-non-standard-port

I would like to be able to configure the internal samba dns server to
listen on a port other than 53 so I can easily interoperate the samba
internal dns with another dns server on the same host.

Many other samba services have configuration to change the default port --
the dns server should as well.