MB-12067: Disable defragmenter by default
MB-12067: Disable defragmenter by default

Disable the Defragmenter task by default, to allow profiling of just
jemalloc compared to tcmalloc, without the defragmenter being in play.

Change-Id: I87d5c15c217f0f53b8a264ccf17377d12f7c7e82
Reviewed-on: http://review.couchbase.org/43242
Reviewed-by: Chiyoung Seo <fcffc23db27b19ee4ebba46695ee6b50e09216a2@couchbase.com>
Tested-by: Chiyoung Seo <fcffc23db27b19ee4ebba46695ee6b50e09216a2@couchbase.com>

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