MB-100: Remove persistence time check from observe test
MB-100: Remove persistence time check from observe test

The persistence time is too difficult to consistenly make
greater than zero. This change removes the check so that the
test case consistently passes.

Change-Id: I851b97af945c85acc0ead3313da8a075cfeceb53
Reviewed-on: http://review.couchbase.org/18722
Tested-by: Chiyoung Seo <8b279095f11c26cc21045fda5a3e51debb005aa9@gmail.com>
Reviewed-by: Chiyoung Seo <8b279095f11c26cc21045fda5a3e51debb005aa9@gmail.com>

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