default.xml: Use Linaro version of vold

Linaro's vold is patched to allow symlinks to be used in vold managed
fstab entries, this is required with device-tree booting where the
real device path is not at a fixed location.

See vold Change-Id: I68e693772e70b758dab22fcd5f0eb4b9e84a2443

Change-Id: I008caa8d152fcb45b8e055e33160b26d7b9840fb
Signed-off-by: Jon Medhurst <tixy@linaro.org>