CBQE-1187 make cbtransfer job working on windows

Change-Id: I90bbdc0480eedf1889c9623c27fb4b3b760c7620
Reviewed-on: http://review.couchbase.org/27075
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Chisheng Hong <chisheng@couchbase.com>