JAVA-1148: Fixed deadlock between DefaultServer and MultiServerCluster by removing unnecessary synchronization in DefaultServer

Author: jyemin

src/main/com/mongodb/DefaultServer.java

@@ -108,7 +108,7 @@ public boolean isClosed() {
 
     private final class DefaultServerStateListener implements ChangeListener<ServerDescription> {
         @Override
-        public synchronized void stateChanged(final ChangeEvent<ServerDescription> event) {
+        public void stateChanged(final ChangeEvent<ServerDescription> event) {
             description = event.getNewValue();
             for (ChangeListener<ServerDescription> listener : changeListeners.keySet()) {
                 listener.stateChanged(event);