Eagerly initialize Netty 4

Today we initialize Netty in a static initializer. We trigger this
method via static initializers from Netty-related classes, but we can
trigger this method earlier than we do to ensure that Netty is
initialized how we want it to be.

modules/transport-netty4/src/main/java/org/elasticsearch/transport/Netty4Plugin.java

@@ -32,6 +32,7 @@ import org.elasticsearch.plugins.NetworkPlugin;
 import org.elasticsearch.plugins.Plugin;
 import org.elasticsearch.threadpool.ThreadPool;
 import org.elasticsearch.transport.netty4.Netty4Transport;
+import org.elasticsearch.transport.netty4.Netty4Utils;
 
 import java.util.Arrays;
 import java.util.Collections;
@@ -41,6 +42,10 @@ import java.util.function.Supplier;
 
 public class Netty4Plugin extends Plugin implements NetworkPlugin {
 
+    static {
+        Netty4Utils.setup();
+    }
+
     public static final String NETTY_TRANSPORT_NAME = "netty4";
     public static final String NETTY_HTTP_TRANSPORT_NAME = "netty4";