gnome-disk-utility: backport property DeviceAutomountHint

Currently we have gvfs 1.10.1 which was designed for gnome-disk-utility 3.x.
We have a patched gvfs so that it works with gnome-disk-utility 2.x but that
does not support the property DeviceAutomountHint because it was introduced in
3.x.

Fixes warnings as:

| (palimpsest:829): libgdu-WARNING **: unhandled property 'DeviceAutomountHint'

Signed-off-by: Andreas Müller <schnitzeltony@googlemail.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>