test: fix flaky interop tests - address already in use

[dozyio]

Description

Inerop tests were intermittently failing - primarily due to bind: address already in use.

Should hopefully fix some of the flaky tests from here #3387

Change checklist

• I have performed a self-review of my own code
• I have made corresponding changes to the documentation if necessary (this includes comments as well)
• I have added tests that prove my fix is effective or that my feature works

[achingbrain]

It would be nice to understand why this is happening and fix the root cause, rather than masking it with retries?

[dozyio]

It would be nice to understand why this is happening and fix the root cause, rather than masking it with retries?

It due to the control port number being assigned ahead of time that clashes when tests are run... seems there is around a 6% chance that ports will clash.

Looked at a few different ways to do it but p2pd doesn't output the actual control port that is used, only the inputted string, so can't pass in 0.

I've updated the PR to use unix domain sockets on non-windows for control instead.

Windows still uses TCP but pre-binds to a port to get an available number