BTSync fix for missing add folder dialog

I hope this works ... tested it on my DS413j.

Sources:
- https://github.com/SynoCommunity/spksrc/issues/1229#issuecomment-55250139
- http://forum.bittorrent.com/topic/31586-synologynastentative-solution-to-resolve-cannot-accept-eula-cannot-see-folders-in-add-folder-view/