The whole point of using `proc_open()` to execute `openssl s_client` is
that we can terminate the process when we're done.  However, when going
through the shell on Windows, we get a handle to the shell process, and
if we terminate that, the grandchild will stay open.  Since the pipes
of the grandchild will stay open, the PHP process will not terminate
either, so the test stalls.

We solve this by simply bypassing the shell.