The type of connection_id for killCursors events differs depending on server version

killCursors events for MongoDB >= 3.2 publish connection_id as an instance of tuple. For MongoDB < 3.2 connection_id is published as an internal type, _CursorAddress, a subclass of tuple with an extra attribute.

This was uncovered by a test failure under Jython, which appears to consider exact subclass in comparisons:

======================================================================

FAIL: test_kill_cursors (test.test_monitoring.TestCommandMonitoring)

----------------------------------------------------------------------

Traceback (most recent call last):

  File "test/test_monitoring.py", line 508, in test_kill_cursors

    self.assertEqual(cursor.address, started.connection_id)

AssertionError: (u'localhost', 27017) != (u'localhost', 27017)

We'll fix this by always publishing a tuple, rather than the subclass, to match the rest of the monitoring API. This change could be a backward breaking change for some application somewhere (though that's extremely unlikely).