Bug 1078128 - [Settings] remove try_show_homescreen_section.js and move this logic into root.js

...to root.js
By doing this we do not have the flexibility of controlling the timing of calling to `mgmt.getAll`. If `mgmt.getAll` is very expensive, we may not want to call it until `onBeforeShow` or `onShow`.
Therefore the best timing of calling to `mgmt.getAll` would be the first time `apps` gets called.