fix: don't reset monitor if we aren't streaming topology changes

A race condition exists when resetting the server monitor during
an existing server check. The reset is not required when we are
not streaming topology changes, so the fix is to no-op in that
condition.

NODE-2876

Author: mbroadst

lib/core/sdam/monitor.js

@@ -118,7 +118,8 @@ class Monitor extends EventEmitter {
   }
 
   reset() {
-    if (isInCloseState(this)) {
+    const topologyVersion = this[kServer].description.topologyVersion;
+    if (isInCloseState(this) || topologyVersion == null) {
       return;
     }
 
@@ -152,7 +153,6 @@ class Monitor extends EventEmitter {
 }
 
 function resetMonitorState(monitor) {
-  stateTransition(monitor, STATE_CLOSING);
   if (monitor[kMonitorId]) {
     monitor[kMonitorId].stop();
     monitor[kMonitorId] = null;