Bug 1061519 Fixes jshint error in tests/atoms/gaia_apps.js r=yurenju

we should fix the warning on line 217, using `Object.keys()` can get an array for properties, so please remove `jshint -W098` and function `numRunningApps` on lin 214~221 can be rewrote like: 

```js
  numRunningApps: function(includeSystemApps) {
    return Object.keys(GaiaApps.getApps(includeSystemApps));
  },
```