Merge lp://qastaging/~nik90/ubuntu-clock-app/fix-alarm-sound-race-issue into lp://qastaging/ubuntu-clock-app

Fixes race issue in the edit alarm page caused due to the QML FolderListModel resulting in incorrect alarm sound names sometimes being shown.

In trunk, there is a race issue involved due the 2 QML FolderListModels defaultSoundModel and customSoundModel. The reason it happens is because QML FolderListModel does not have a signal to indicate that it has finished loading. The onComplete() signal is useless here since after it has completed, the count variable still takes another few ms to update.

So some of the file checks we do for custom alarm sound like checking the existence of the file is done *before* the 2 FolderListModels have fully loaded thereby providing incorrect results sometimes.

I have introduced a Timer which introduces a delay of 250ms to ensure that the FolderListModels have fully loaded before performing the file checks.

This seems to have solved the issue.