CBQE-2141: fix is_couchbase_installed for windows

we shouldn't check if couchbase running in this func

Change-Id: I1c100c30f3c901466a8b00c8562310d15fc476c1
Reviewed-on: http://review.couchbase.org/34923
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>
Tested-by: Andrei Baranouski <andrei.baranouski@gmail.com>