PYTHON-2074 Correctly mock the MonitorBase API

Author: prashantmital

test/test_discovery_and_monitoring.py

@@ -46,13 +46,13 @@ def __init__(self, server_description, topology, pool, topology_settings):
     def open(self):
         pass
 
-    def request_check(self):
+    def close(self):
         pass
 
-    def close(self):
+    def join(self):
         pass
 
-    def remove_stale_sockets(self, reference_pool_id):
+    def request_check(self):
         pass