Wrong transpilation for renamed import

Given this reproduction file: https://github.com/simonihmig/ember-warn-transpilation/blob/master/app/utils/warn.js

This is transpiled to:
```js
define('ember-warn-transpilation/utils/warn', ['exports'], function (exports) {
'use strict';

Object.defineProperty(exports, "__esModule", {
value: true
});
exports.default = warn;
function warn() {
(true && Ember.emberWarn(...arguments));
}
});
```

Where `Ember.emberWarn` is obviously not a thing.