fix(sessions): actually allow ending of sessions

Currently, endSessions filters out any calls that happen while
the topology is connected. However, it is impossible to send
an endSessions command if you are not connected. This fix allows
sessions to be ended while the topology is connected

Part of HELP-5834

lib/topologies/shared.js

@@ -378,11 +378,6 @@ function resolveClusterTime(topology, $clusterTime) {
 //       to share code.
 const SessionMixins = {
   endSessions: function(sessions, callback) {
-    if (this.isConnected()) {
-      if (typeof callback === 'function') callback();
-      return;
-    }
-
     if (!Array.isArray(sessions)) {
       sessions = [sessions];
     }
@@ -395,7 +390,7 @@ const SessionMixins = {
     //   Is it enough to use: ReadPreference.primaryPreferred ?
     this.command(
       'admin.$cmd',
-      { endSessions: sessions.map(s => s.id) },
+      { endSessions: sessions },
       { readPreference: ReadPreference.primaryPreferred },
       () => {
         // intentionally ignored, per spec