CBQE-2451 add auto install for sherlock on centos 6
in testrunner

Change-Id: I8f319949667f8f4d2ace178cc1312aeb435468ff
Reviewed-on: http://review.couchbase.org/42584
Reviewed-by: Thuan Nguyen <soccon@gmail.com>
Tested-by: Thuan Nguyen <soccon@gmail.com>