tests: testrunner reliability improvements

tests: testrunner reliability improvements

- perform torture tests with '-j2' for shorter runtime
- when waiting on test results overly long, log the tests
  waited for and eventually log the test log directories
  for easier analysis what is wrong in CI jobs.
- sockfilt.c: treat the windows errno 109 (ERROR_BROKEN_PIPE)
  as a socket closed by the client and do not exit.
- when verifying https server, do not in addition check
  the http server behind it also
- when tearing down the stunnel of a non-responsive https
  server, tear down the http server with it

Closes #14960