add 2i stats collection in secondary indexing tests
add 2i stats collection in secondary indexing tests

Change-Id: Ie1e297c76e73efecf2098825edabf548bb83f948
Reviewed-on: http://review.couchbase.org/50562
Tested-by: buildbot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Reviewed-by: Venu Uppalapati <5c73d43f38c8de2bc4a2e4d15365e52f60b59dae@gmail.com>

couchbase/perfrunner,pavel-paulau/perfrunner,vmx/perfrunner,pavel-paulau/perfrunner,hsharsha/perfrunner,vmx/perfrunner,pavel-paulau/perfrunner,couchbase/perfrunner,thomas-couchbase/perfrunner,thomas-couchbase/perfrunner,PaintScratcher/perfrunner,dkao-cb/perfrunner,pavel-paulau/perfrunner,mikewied/perfrunner,EricACooper/perfrunner,EricACooper/perfrunner,hsharsha/perfrunner,PaintScratcher/perfrunner,couchbase/perfrunner,EricACooper/perfrunner,couchbase/perfrunner,EricACooper/perfrunner,couchbase/perfrunner,dkao-cb/perfrunner,mikewied/perfrunner,couchbase/perfrunner,pavel-paulau/perfrunner