Bug 879187 - Re-render suggestion list after switching to new keyboard type

Fix for [#879187](https://bugzilla.mozilla.org/show_bug.cgi?id=879187). At the moment the suggestion list disappears because the complete keyboard layout gets [re-rendered](https://github.com/mozilla-b2g/gaia/blob/master/apps/keyboard/js/render.js#L157). This patch instructs the worker to re-render the list of suggestions after keyboard has been switched.