bug#30807: Tramp tests take waaayyy too long and refuse to exit

[Glenn Morris]

With current master, tramp-archive-tests are very slow.
My time to run "make -j8 check" is 3 minutes.
If I remove tramp-archive-tests.el, it changes to 30 seconds.

Here are the slowest tests. Perhaps anything that takes more than 10
seconds should be tagged expensive?


LONG-RUNNING TESTS
------------------
   passed  10/22  tramp-archive-test11-copy-file (30.784306 sec)
   passed  11/22  tramp-archive-test15-copy-directory (20.679223 sec)
   passed  12/13  cl-seq-test-bug24264 (15.896021 sec)
   passed  1/3  auto-revert-test00-auto-revert-mode (13.111064 sec)
   passed  22/22  tramp-archive-test43-delay-load (11.372054 sec)
   passed  21/22  tramp-archive-test43-auto-load (11.365802 sec)
   passed  14/22  tramp-archive-test18-file-attributes (10.369735 sec)
   passed   8/22  tramp-archive-test08-file-local-copy (10.309309 sec)
   passed  13/22  tramp-archive-test17-insert-directory (10.301208 sec)
   passed  17/22  tramp-archive-test21-file-links (10.298635 sec)
   passed  18/22  tramp-archive-test26-file-name-completion (10.280112 sec)
   passed  16/22  tramp-archive-test20-file-modes (10.269900 sec)
   passed  15/22  tramp-archive-test19-directory-files-and-attributes 
(10.256971 sec)
   passed  12/22  tramp-archive-test16-directory-files (10.250864 sec)
   passed   7/22  tramp-archive-test07-file-exists-p (10.171281 sec)
   passed   9/22  tramp-archive-test09-insert-file-contents (10.160516 sec)
   passed  3/3  auto-revert-test04-auto-revert-mode-dired (6.042494 sec)
   passed  5/8  file-notify-test04-autorevert (6.017824 sec)
   passed  1/2  inotify-file-watch-simple (5.002061 sec)