CBQE-0 : taskkill command not found

Change-Id: I0624058fb981f90269904dd37e4059161871d7ec
Reviewed-on: http://review.couchbase.org/38656
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>
Reviewed-by: Meenakshi Goel <meenakshi.goel@globallogic.com>
Tested-by: Meenakshi Goel <meenakshi.goel@globallogic.com>