MB-18286: Enable sequence iteration in forestdb
MB-18286: Enable sequence iteration in forestdb

For streaming out vbucket mutations over DCP streams, we need
to iterate them by sequence number. This requires the underlying
storage engine (forestdb) to support by-sequence indexing & iteration.
So we must set this option to SEQTREE_USE since it is not the default
option in forestdb.


Change-Id: Ie9f93c8cb245fd7f106da9118da642061979fcc2
Reviewed-on: http://review.couchbase.org/60954
Reviewed-by: Sriram Ganesan <fde85c3124eed34938bb85159f430bf7e5b650f6@couchbase.com>
Tested-by: buildbot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>

membase/ep-engine,membase/ep-engine,teligent-ru/ep-engine,couchbase/ep-engine,hisundar/ep-engine,daverigby/ep-engine,daverigby/kv_engine,teligent-ru/ep-engine,couchbase/ep-engine,owendCB/ep-engine,membase/ep-engine,daverigby/kv_engine,hisundar/ep-engine,owendCB/ep-engine,teligent-ru/ep-engine,daverigby/ep-engine,hisundar/ep-engine,owendCB/ep-engine,hisundar/ep-engine,daverigby/ep-engine,couchbase/ep-engine,daverigby/ep-engine,teligent-ru/ep-engine,daverigby/kv_engine,couchbase/ep-engine,membase/ep-engine,owendCB/ep-engine,daverigby/kv_engine