Windows: Prevent tools from clashing with named in system tests

In system tests on Windows tool's local port can sometimes clash with 'named'. On Unix the system is poked for the minimal local port, otherwise is set to 32768 as a sane minimum. For Windows we don't poke but set a hardcoded limit; this change aligns the limit with Unix and changes it to 32768.

Closes #1566 (closed).