CBQE-1212 add swappiness params in unix installation script

Change-Id: I09c66358fb4febca8c055a9a5a87be45628d8e9c
Reviewed-on: http://review.couchbase.org/25642
Tested-by: Thuan Nguyen <soccon@gmail.com>
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Tommie McAfee <tommie@couchbase.com>