make sysinfo provider a setting

src/sysinfo/generic.js

@@ -1,7 +1,7 @@
 'use strict';
 
 exports = module.exports = {
-    getPublicIp: getPublicIp
+    getServerIp: getServerIp
 };
 
 var assert = require('assert'),
@@ -9,7 +9,8 @@ var assert = require('assert'),
     BoxError = require('../boxerror.js'),
     superagent = require('superagent');
 
-function getPublicIp(callback) {
+function getServerIp(config, callback) {
+    assert.strictEqual(typeof config, 'object');
     assert.strictEqual(typeof callback, 'function');
 
     if (process.env.BOX_ENV === 'test') return callback(null, '127.0.0.1');