Setting exists equals false instead of not exists

This commit rewrites a boolean expression to check for equality with
false instead of negating the existence check.

client/transport/src/main/java/org/elasticsearch/transport/client/PreBuiltTransportClient.java

@@ -91,7 +91,7 @@ public class PreBuiltTransportClient extends TransportClient {
     @Override
     public void close() {
         super.close();
-        if (!NetworkModule.TRANSPORT_TYPE_SETTING.exists(settings)
+        if (NetworkModule.TRANSPORT_TYPE_SETTING.exists(settings) == false
             || NetworkModule.TRANSPORT_TYPE_SETTING.get(settings).equals(Netty4Plugin.NETTY_TRANSPORT_NAME)) {
             try {
                 GlobalEventExecutor.INSTANCE.awaitInactivity(5, TimeUnit.SECONDS);