CLOUD: Saves sync triggered twice in a row after saving

[bgK]

ScummVM 4810a5d8d35c5caa79f9a3a1e93d882de32b2d87.

Saving in Myst produces 2 files. The Cloud save sync process is triggered twice after saving. This causes poor user experience on systems with slow IO as the main thread freezes for a while when starting the sync process.

It's not uncommon for engines to modify multiple files when saving. Perhaps there should be a delay between the moment a save file is written and starting the save sync process so that if the engine modifies multiples files they are synced all at once.