PYTHON-3174 Remove noisy running Topology check for main test client

[ShaneHarvey]

This change avoids false positives for the main client_context client. I also changed the output to be a little more readable. When the check finds a real problem, the new output looks like this:

pypy3 setup.py test -s test.test_client.TestClient
...
test_waitQueueTimeoutMS (test.test_client.TestClient) ... ok
----------------------------------------------------------------------
Ran 57 tests in 19.489s

OK (skipped=9)
WARNING: found Topology with running threads:
  Threads: [<PeriodicExecutor(name=pymongo_server_monitor_thread) object at 0x7facb8231248>, <PeriodicExecutor(name=pymongo_server_rtt_thread) object at 0x7facb8231328>]
  Topology: <Topology <TopologyDescription id: 6230fe16efe40a2b8ad01304, topology_type: ReplicaSetWithPrimary, servers: [<ServerDescription ('localhost', 27017) server_type: RSPrimary, rtt: 0.007118122831045185>]>>
  Creation traceback:
  File "setup.py", line 345, in <module>
    **extra_opts
  File "/usr/local/Cellar/pypy3/7.3.4/libexec/site-packages/setuptools-54.2.0-py3.7.egg/setuptools/__init__.py", line 153, in setup
    return distutils.core.setup(**attrs)
  File "/usr/local/Cellar/pypy3/7.3.4/libexec/lib-python/3/distutils/core.py", line 148, in setup
    dist.run_commands()
  File "/usr/local/Cellar/pypy3/7.3.4/libexec/lib-python/3/distutils/dist.py", line 966, in run_commands
    self.run_command(cmd)
  File "/usr/local/Cellar/pypy3/7.3.4/libexec/lib-python/3/distutils/dist.py", line 985, in run_command
    cmd_obj.run()
  File "setup.py", line 122, in run
    result = runner.run(suite)
  File "/Users/shane/git/mongo-python-driver/test/__init__.py", line 1095, in run
    result = super(PymongoTestRunner, self).run(test)
  File "/usr/local/Cellar/pypy3/7.3.4/libexec/lib-python/3/unittest/runner.py", line 176, in run
    test(result)
  File "/usr/local/Cellar/pypy3/7.3.4/libexec/lib-python/3/unittest/suite.py", line 84, in __call__
    return self.run(*args, **kwds)
  File "/usr/local/Cellar/pypy3/7.3.4/libexec/lib-python/3/unittest/suite.py", line 122, in run
    test(result)
  File "/usr/local/Cellar/pypy3/7.3.4/libexec/lib-python/3/unittest/case.py", line 676, in __call__
    return self.run(*args, **kwds)
  File "/usr/local/Cellar/pypy3/7.3.4/libexec/lib-python/3/unittest/case.py", line 628, in run
    testMethod()
  File "/Users/shane/git/mongo-python-driver/test/__init__.py", line 556, in wrap
    return f(*args, **kwargs)
  File "/Users/shane/git/mongo-python-driver/test/test_client.py", line 1279, in test_exhaust_network_error
    client = rs_or_single_client(maxPoolSize=1, retryReads=False)
  File "/Users/shane/git/mongo-python-driver/test/utils.py", line 565, in rs_or_single_client
    return _mongo_client(h, p, **kwargs)
  File "/Users/shane/git/mongo-python-driver/test/utils.py", line 529, in _mongo_client
    return MongoClient(uri, port, **client_options)
  File "/Users/shane/git/mongo-python-driver/pymongo/mongo_client.py", line 785, in __init__
    srv_max_hosts=srv_max_hosts,
  File "/Users/shane/git/mongo-python-driver/pymongo/settings.py", line 77, in __init__
    self._stack = "".join(traceback.format_stack())

[blink1073]

LGTM!