networking.save_texture should return image buffer, not lwip image object

This led to a crash when a cape or skin was not stored on disk.
The function caled skins.save_image and returned that function's lwip image object instead of the expected buffer.
skins.save_image also no longer returns the image object because it's not used anywhere

lib/routes/skins.js

@@ -1,4 +1,3 @@
-var logging = require("../logging");
 var helpers = require("../helpers");
 var skins = require("../skins");
 var cache = require("../cache");