CBQE-0 fix os type selection

Change-Id: I8a60438dcc021ec622ba15179d4e17a5b5f9273d
Reviewed-on: http://review.couchbase.org/44020
Reviewed-by: Thuan Nguyen <soccon@gmail.com>
Tested-by: Thuan Nguyen <soccon@gmail.com>