Remove nbd, already upstream

Signed-off-by: David Scott <dave.scott@citrix.com>
Remove xenctrl, upstream now

Signed-off-by: David Scott <dave.scott@citrix.com>
Remove vhdlib, now upstream

Signed-off-by: David Scott <dave.scott@citrix.com>
Merge pull request #45 from djs55/remove-upstream

Remove upstreamed packages