[virt-tools-list] [PATCH v2 virt-viewer] Shift top-left display to origin

[Jonathon Jongsma]

Changes since v1:
- split into 2 patches
- fixed wording ("shift down" -> "shift")
- remove unnecessary check for disabled displays, since these rects were
  actually client monitor geometries which can't be disabled.
- re-word function comment slightly