Not free external allocated memory blocks.

The pointer wsi->user_space is an external allocated memory block.
For caller (the user of libwebsocket), it will be clearer ownership that libwebsocket don’t free it but let the owner do handling the cleanup and free.
If you want to allocate this data yourself you should set the ```per_session_data_size``` to 0 when defining your websocket protocol, otherwise libwebsocket will allocate this memory for you, and hence free it here.