Fix "make test-stem" after merging #32339 and #32344

In legacy/trac#32339 (moved) and legacy/trac#32344 (moved), we broke "make test-stem", but we didn't notice before merging, because "make test-stem" is allow_failure in Travis CI.

It looks like we need to get stem to launch a new tor process for more tests. Or our immutability checks are too strict.

Here is one of the errors:

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FAIL: test_take_ownership_via_controller
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Traceback (most recent call last):
  File "/home/dev/stem/stem/util/test_tools.py", line 152, in <lambda>
    self.method = lambda test: self.result(test)  # method that can be mixed into TestCases
  File "/home/dev/stem/stem/util/test_tools.py", line 227, in result
    test.fail(self._result.msg)
AssertionError: Traceback (most recent call last):
  File "/home/dev/stem/stem/util/test_tools.py", line 169, in _wrapper
    runner(*args) if args else runner()
  File "/home/dev/stem/test/integ/process.py", line 641, in test_take_ownership_via_controller
    take_ownership = True,
  File "/home/dev/stem/stem/process.py", line 285, in launch_tor_with_config
    return launch_tor(tor_cmd, ['-f', '-'], None, completion_percent, init_msg_handler, timeout, take_ownership, close_output, stdin = config_str)
  File "/home/dev/stem/stem/process.py", line 158, in launch_tor
    raise OSError('Process terminated: %s' % last_problem)
OSError: Process terminated: Failed to bind one of the listener ports.


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