Fix StandardServerSocket.isClosed() and close()

thx cacapo
ref: http://zzz.i2p/topics/1547

apps/streaming/java/src/net/i2p/client/streaming/impl/StandardServerSocket.java

@@ -137,7 +137,7 @@ class StandardServerSocket extends ServerSocket {
 
     @Override
     public boolean isClosed() {
-        return ((I2PSocketManagerFull)_socket.getManager()).getConnectionManager().getAllowIncomingConnections();
+        return !((I2PSocketManagerFull)_socket.getManager()).getConnectionManager().getAllowIncomingConnections();
     }
 
     /**