fix duplicate element creation when wrapping the bootstrap list (#1532)

closes #1530

src/main/java/com/comphenix/protocol/injector/netty/manager/ListeningList.java

@@ -18,6 +18,9 @@ final class ListeningList implements List<Object> {
 	public ListeningList(List<Object> original, ChannelHandler channelHandler) {
 		this.original = original;
 		this.channelHandler = channelHandler;
+
+		// no need to copy all elements of the original list, but we need to inject them
+		original.forEach(this::processInsert);
 	}
 
 	@Override

src/main/java/com/comphenix/protocol/injector/netty/manager/NetworkManagerInjector.java

@@ -204,11 +204,8 @@ public class NetworkManagerInjector implements ChannelListener {
 				// we need to synchronize accesses to the list ourselves, see Collections.SynchronizedCollection
 				//noinspection SynchronizationOnLocalVariableOrMethodParameter
 				synchronized (value) {
-					// then copy all old values into the new list
+					// override the list field with our list
 					List<Object> newList = Collections.synchronizedList(new ListeningList(value, this.pipelineInjectorHandler));
-					newList.addAll(value);
-
-					// rewrite the actual field
 					accessor.set(serverConnection, newList);
 				}
 			}