qemu-dm-wrapper: the is_sdk(), fake_dm() stuff is redundant
qemu-dm-wrapper: cleanup() is dead code, so clean it up
qemu-dm-wrapper: do_closec() was dead code, clean it up
qemu-dm-wrapper: avoid using the 'xen' python module (since it doesn't exist on modern xen installs) and shell out to 'xenstore-write' instead.