CBQE-0 kill all previous rpm process before uninstall cb

Change-Id: I98631ca02113e7615f21ac12a56bac2b8dec660f
Reviewed-on: http://review.couchbase.org/43491
Tested-by: Thuan Nguyen <soccon@gmail.com>
Reviewed-by: Aruna Piravi <aruna@couchbase.com>