Hung up on writing Unit tests for dynamic DNS update from different source addresses

[Matt Grant]

Hi!

Code as it is up in merge request:
https://gitlab.com/samba-team/samba/-/merge_requests/2271

It's come a long way.  Been cleaned up a lot, and just completing the test
suite.  Need to test
denying DNS update by IP source address, and updates authed by IP source
address.

Have managed to update dns_base.py to optionally bind to a source IP
address for a query, but can't figure how to
set SOCKET_WRAPPER_DEFAULT_IFACE for the test/special test suite process
socket wrapper stuff.  Tis getting quite seeing double inside
selftest/target/Samba4.pm and source4/selftest/tests.py....

Could some one please lay out a map for me how to proceed with this, or
just help me to give it this extra push with this to get this over the hump
and accepted for merging?

Thank you!

Matt Grant