Revert all settings stealing code

Revert all settings stealing code

This patch accompanies commit bf92f4b7 to XENVIF. That patch reverts
XENVIF to using the settings copy mechanism employed in the 8.1 driver,
so this patch accordingly removes all relevant modifications to the
XENNET co-installer.

The patches reverted are:

9695e3bd "Re-instate code network settings code in the co-installer"
59901522 "Remove code to clear stolen stack binding"
ed747f69 "Clear stolen linkage on device removal"

Signed-off-by: Paul Durrant <paul.durrant@citrix.com>