MB-5208 Process the TAP BG fetch failures correctly
MB-5208 Process the TAP BG fetch failures correctly

TAP BG fetch failures should be separated from the success cases
and should be logged with more information.

Change-Id: I47faea15c694166b7e338daff27b09afbd798c1c
Reviewed-on: http://review.couchbase.org/15695
Reviewed-by: Jin Lim <c45cd80a556f432a3607171a6818cd5a074b5cd4@couchbase.com>
Tested-by: Chiyoung Seo <8b279095f11c26cc21045fda5a3e51debb005aa9@gmail.com>
Reviewed-on: http://review.couchbase.org/15838
Reviewed-by: Chiyoung Seo <8b279095f11c26cc21045fda5a3e51debb005aa9@gmail.com>

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