pgsql: Probe only 127.0.0.1 when looking for ports on Unix.

Probe only 127.0.0.1 when looking for ports on Unix.

Commit c0985099, later adjusted by commit 4ab02e81, probed 0.0.0.0
in addition to 127.0.0.1, for the benefit of Windows build farm
animals.  It isn't really useful on Unix systems, and turned out to
be a bit inconvenient to users of some corporate firewall software.
Switch back to probing just 127.0.0.1 on non-Windows systems.

Back-patch to 9.6, like the earlier changes.

Discussion: https://postgr.es/m/CA%2BhUKG%2B21EPwfgs4m%2BtqyRtbVqkOUvP8QQ8sWk9%2Bh55Aub1H3A%40mail.gmail.com

Branch
------
REL9_6_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/1ed42e50e9636f5c9c86c679afee9200ca4e2323

Modified Files
--------------
src/test/perl/PostgresNode.pm | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)