Adapt to the new ChannelFactory/ServerChannelFactory

[violetagg]

In Netty 5 we have now

/**
 * Creates a new {@link Channel}.
 */
public interface ChannelFactory<T extends Channel> {
    /**
     * Creates a new channel.
     */
    T newChannel(EventLoop eventLoop) throws Exception;
}

/**
 * Creates a new {@link ServerChannel}.
 */
public interface ServerChannelFactory<T extends ServerChannel> {
    /**
     * Creates a new channel.
     */
    T newChannel(EventLoop eventLoop, EventLoopGroup childEventLoopGroup) throws Exception;
}

Related to #1873

[pderop]

LGTM

[violetagg]

@pderop Thanks for the review