postgres_fdw test timeouts

I noticed that the postgres_fdw test periodically times out on Windows:

    https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=fairywren&dt=2023-11-10%2003%3A12%3A58
    https://cirrus-ci.com/task/5504294095421440
    https://cirrus-ci.com/task/4814111003901952
    https://cirrus-ci.com/task/5343037535027200
    https://cirrus-ci.com/task/5893655966253056
    https://cirrus-ci.com/task/4568159320014848
    https://cirrus-ci.com/task/5238067850641408
    (and many more from cfbot)

From a quick sampling, the relevant test logs end with either

    ERROR:  server "unknownserver" does not exist
    STATEMENT:  SELECT postgres_fdw_disconnect('unknownserver');

or

    ERROR:  relation "public.non_existent_table" does not exist
    CONTEXT:  remote SQL command: SELECT a, b, c FROM public.non_existent_table
    STATEMENT:  SELECT * FROM async_pt;

before the test seems to hang.

AFAICT the failures began around September 10th, which leads me to wonder
if this is related to commit 04a09ee.  That is little more than a wild
guess, though.  I haven't been able to deduce much else from the logs I can
find, and I didn't find any previous reports about this in the archives
after lots of searching, so I thought I'd at least park these notes here in
case anyone else has ideas.

-- 
Nathan Bossart
Amazon Web Services: https://aws.amazon.com