[#2605] Use SO_REUSEADDR on EpollServerSocketChannel to match defaults of java.nio.ServerSocketChannel impl

Motivation:

When using openjdk and oracle jdk's nio (while using the nio transport) the ServerSocketChannel uses SO_REUSEADDR by default. Our native transport should do the same to make it easier to switch between the different implementations and get the expected result.

Modification:

Change EpollServerSocketChannelConfig to set SO_REUSEADDR on the created socket.

Result:

SO_REUSEADDR is used by default on servers.

transport-native-epoll/src/main/java/io/netty/channel/epoll/EpollServerSocketChannelConfig.java

@@ -38,6 +38,11 @@ public final class EpollServerSocketChannelConfig extends DefaultChannelConfig
     EpollServerSocketChannelConfig(EpollServerSocketChannel channel) {
         super(channel);
         this.channel = channel;
+
+        // Use SO_REUSEADDR by default as java.nio does the same.
+        //
+        // See https://github.com/netty/netty/issues/2605
+        setReuseAddress(true);
     }
 
     @Override