Do not check the shuwdown event before every FTS operation
Do not check the shuwdown event before every FTS operation

It's a rather expensive operation and it should only be performed
once per batch (in run method).

Change-Id: I066aa672402e832bb8eabd0dea427f214a73f7bf
Reviewed-on: http://review.couchbase.org/76063
Tested-by: Build Bot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Reviewed-by: Alex Gyryk <0e5cab161284683621f17481c0995df0d35b63eb@couchbase.com>

pavel-paulau/perfrunner,pavel-paulau/perfrunner,couchbase/perfrunner,pavel-paulau/perfrunner,couchbase/perfrunner,couchbase/perfrunner,couchbase/perfrunner,couchbase/perfrunner,pavel-paulau/perfrunner,pavel-paulau/perfrunner,couchbase/perfrunner