interactive: reset tiled state when dragging out of snapped position

interactive: reset tiled state when dragging out of snapped position

This ensures that client-side decorations (and maybe other client
behaviors) behave intuitively during interative moves, but means that

    drag to snapped position -> drag to maximize -> un-maximize

will put the window back to its natural geometry (saved before the first
snap) rather than back to the snapped position. This is a change in
behavior, but a) simplifies the logic a bit, because the tiled state is
always in sync with the window geometry and b) in some sense is "more
correct", because the window has been "visually" un-tiled the minute the
window starts dragging.

Note that maximizing using an action (including the button) a window
that has been snapped and then un-maximizing the window will put the
window back to the snapped position, as it always has.