Free port choosing freezes when PostgresNode::use_tcp is used on BSD systems

Hi Hackers,

Inside PostgresNode.pm there is a free port choosing routine ---
get_free_port(). The comment section there says:

# On non-Linux, non-Windows kernels, binding to 127.0.0/24 addresses
# other than 127.0.0.1 might fail with EADDRNOTAVAIL.

And this is an absolute true, on BSD-like systems (macOS and FreeBSD
tested) it hangs on looping through the entire ports range over and over
when $PostgresNode::use_tcp = 1 is set, since bind fails with:

# Checking port 52208
# bind: 127.0.0.1 52208
# bind: 127.0.0.2 52208
bind: Can't assign requested address

To reproduce just apply reproduce.diff and try to run 'make -C
src/bin/pg_ctl check'.

This is not a case with standard Postgres tests, since TestLib.pm
chooses unix sockets automatically everywhere outside Windows. However,
we got into this problem when tried to run a custom tap test that
required TCP for stable running.

That way, if it really could happen why not to just skip binding to
127.0.0/24 addresses other than 127.0.0.1 outside of Linux/Windows as
per attached patch_PostgresNode.diff?

Regards
--
Alexey Kondratov

Postgres Professional https://www.postgrespro.com
Russian Postgres Company