Relocating chunks during chunk loading does not actually relocate the chunk

MCP deobfuscated code from AnvilChunkLoader.checkedReadChunkFromNBT at https://gist.github.com/nallar/5259703.

This is setting xPos/zPos in the root NBTTagCompound, it should be set in the Level NBTTagCompound. Additionally, the logic of loading the chunk, then checking coordinates seems odd - why not check and fix the coordinates before loading it? Loading it twice if the coordinates are wrong doesn't seem necessary.

Fixed MCP deobfuscated code at https://gist.github.com/nallar/5259722