Copy the resolver configuration when cloning Bootstrap

Motivation:

Bootstrap.clone() does not copy the resolver configuration.

Modifications:

Copy the resolver configuration when cloning.

Result:

Bug fixed

transport/src/main/java/io/netty/bootstrap/Bootstrap.java

@@ -58,6 +58,7 @@ public class Bootstrap extends AbstractBootstrap<Bootstrap, Channel> {
 
     private Bootstrap(Bootstrap bootstrap) {
         super(bootstrap);
+        resolver = bootstrap.resolver;
         remoteAddress = bootstrap.remoteAddress;
     }