CBLT-42:  replace "cp" with "copy" for windows

Change-Id: I45cfcd73ed6f1ee582502bb6b756257e347971ad
Reviewed-on: http://review.couchbase.org/37227
Reviewed-by: Philip Labee <philip@couchbase.com>
Tested-by: Philip Labee <philip@couchbase.com>