pgsql: Fix buildfarm error from commit 5c31669058.

Fix buildfarm error from commit 5c31669058. Skip test when not using unix domain sockets. Discussion: https://postgr.es/m/caldanm29-8oozsbwo9h6dn_tb_3ya1qjrjput-khan8ncdj...@mail.gmail.com Backpatch-through: 16 Branch -- REL_16_STABLE Details --- https://git.postgresql.org/pg/commitdif

pgsql: Fix buildfarm error from commit 5c31669058.

Fix buildfarm error from commit 5c31669058. Skip test when not using unix domain sockets. Discussion: https://postgr.es/m/caldanm29-8oozsbwo9h6dn_tb_3ya1qjrjput-khan8ncdj...@mail.gmail.com Backpatch-through: 16 Branch -- master Details --- https://git.postgresql.org/pg/commitdiff/dd3ca