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

src/test/perl/PostgresNode.pm

@@ -1101,14 +1101,15 @@ sub get_new_node
 		# This seems like a good idea on Unixen as well, even though we don't
 		# ask the postmaster to open a TCP port on Unix.  On Non-Linux,
 		# non-Windows kernels, binding to 127.0.0.1/24 addresses other than
-		# 127.0.0.1 fails with EADDRNOTAVAIL.
+		# 127.0.0.1 might fail with EADDRNOTAVAIL.  Binding to 0.0.0.0 is
+		# unnecessary on non-Windows systems.
 		#
 		# XXX A port available now may become unavailable by the time we start
 		# the postmaster.
 		if ($found == 1)
 		{
-			foreach my $addr (qw(127.0.0.1 0.0.0.0),
-				$use_tcp ? qw(127.0.0.2 127.0.0.3) : ())
+			foreach my $addr (qw(127.0.0.1),
+				$use_tcp ? qw(127.0.0.2 127.0.0.3 0.0.0.0) : ())
 			{
 				can_bind($addr, $port) or $found = 0;
 			}