refactor: wait until server destroyed before stopping event relay

Some monitoring events (such as connection pool closed, or a return
of a connection to the pool) are desired _after_ a server has been
closed/destroyed.

Author: mbroadst

lib/core/sdam/topology.js

@@ -53,13 +53,7 @@ const SERVER_RELAY_EVENTS = [
 ].concat(CMAP_EVENT_NAMES);
 
 // all events we listen to from `Server` instances
-const LOCAL_SERVER_EVENTS = SERVER_RELAY_EVENTS.concat([
-  'error',
-  'connect',
-  'descriptionReceived',
-  'close',
-  'ended'
-]);
+const LOCAL_SERVER_EVENTS = ['error', 'connect', 'descriptionReceived', 'close', 'ended'];
 
 const STATE_CLOSING = common.STATE_CLOSING;
 const STATE_CLOSED = common.STATE_CLOSED;
@@ -780,6 +774,7 @@ function destroyServer(server, topology, options, callback) {
       new events.ServerClosedEvent(topology.s.id, server.description.address)
     );
 
+    SERVER_RELAY_EVENTS.forEach(event => server.removeAllListeners(event));
     if (typeof callback === 'function') {
       callback();
     }