It seems some Windows versions requires you to be
an Administrator to manage services. Just google for
"openscmanager access denied windows 2008" or similar.

Fixes golang/go#11156.

Change-Id: I4b09d244a61179ece7a1319234e5c3199423cbe9
Reviewed-on: https://go-review.googlesource.com/10933Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>