MB-10164: log reasons for the shard count choice
MB-10164: log reasons for the shard count choice

Change-Id: Iea57eea88167e1f00949a35051d632c09ec8db5e
Reviewed-on: http://review.couchbase.org/34869
Reviewed-by: Chiyoung Seo <fcffc23db27b19ee4ebba46695ee6b50e09216a2@couchbase.com>
Reviewed-by: abhinav dangeti <d73ef2279de6577f7bf081737ee47554bbb7dc82@couchbase.com>
Tested-by: abhinav dangeti <d73ef2279de6577f7bf081737ee47554bbb7dc82@couchbase.com>

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