Remove various uses of INTERNAL_ERROR

INTERNAL_ERROR now means there really was some internal error

src/sysinfo/ec2.js

@@ -13,7 +13,7 @@ function getPublicIp(callback) {
     assert.strictEqual(typeof callback, 'function');
 
     superagent.get('http://169.254.169.254/latest/meta-data/public-ipv4').timeout(30 * 1000).end(function (error, result) {
-        if (error) return callback(new BoxError(BoxError.INTERNAL_ERROR, error.status ? 'Request failed: ' + error.status : 'Network failure'));
+        if (error && !error.response) return callback(new BoxError(BoxError.NETWORK_ERROR, error));
         if (result.statusCode !== 200) return callback(new BoxError(BoxError.EXTERNAL_ERROR, util.format('%s %j', result.status, result.body)));
 
         callback(null, result.text);