Code review comment for lp://qastaging/~fhd/unity-2d/fix-for-bug-6600100

Superb work Felix. It works reliably here.
If you want to make the code more concise and ultimately less prone to memory leaks you may want to use GObjectScopedPointer from libunity-2d-private/src/gscopedpointer.h
You would use it like the following:

GObjectScopedPointer<GMount> g_volume_get_mount(m_volume);
[...]
if (g_mount_can_unmount(mount.data())) {
[...]