run-tests.py: backout "don't use console for stdin when running in debug mode"

f5842787a958 caused that some kind of interactive debugging no longer was
possible - such as running hg with --debugger in a test run with run-tests.py
--debug .

tests/run-tests.py

@@ -751,8 +751,7 b' def run(cmd, wd, options, replacements):'
     Return a tuple (exitcode, output).  output is None in debug mode."""
     # TODO: Use subprocess.Popen if we're running on Python 2.4
     if options.debug:
-        proc = subprocess.Popen(cmd, shell=True, cwd=wd, stdin=subprocess.PIPE)
-        proc.stdin.close()
+        proc = subprocess.Popen(cmd, shell=True, cwd=wd)
         ret = proc.wait()
         return (ret, None)