Use fuse 2.9.X instead of 3.X

- 3.X is still considered pre-release and we managed to get everything
  to work in 2.9.X, so we may as well stick with stable to lessen
  changes of problems.

- Some kernel release between 3.2 and 3.15 broke readdir() in fuse 3.X,
  but it works fine in 2.9.X.