Added gc comment and removed unneeded toBsonDocument in the listener

Author: rozza

driver-sync/src/test/functional/com/mongodb/client/AbstractSessionsProseTest.java

@@ -94,7 +94,7 @@ public void shouldCreateServerSessionOnlyAfterConnectionCheckout() throws Interr
                             @Override
                             public void commandStarted(final CommandStartedEvent event) {
                                 if (event.getCommand().containsKey("lsid")) {
-                                    lsidSet.add(event.getCommand().getDocument("lsid").toBsonDocument());
+                                    lsidSet.add(event.getCommand().getDocument("lsid"));
                                 }
                             }
                         })

driver-sync/src/test/functional/com/mongodb/client/unified/UnifiedTest.java

@@ -311,6 +311,8 @@ public void cleanUp() {
         if (testDef != null) {
             postCleanUp(testDef);
         }
+        // Ask the JVM to run garbage collection.
+        // This should help with Nettys leak detection
         System.gc();
     }