concurrency: don't skip leader updates in Observe()
concurrency: don't skip leader updates in Observe()

The Get for the leader key will fetch based on the latest revision
instead of the deletion revision, missing leader updates between
the delete and the Get.

Although it's usually safe to skip these updates since they're
stale, it makes testing more difficult and in some cases the
full leader update history is desirable.

mkumatag/etcd,glevand/coreos--etcd,yudai/etcd,rnaveiras/etcd,coreos/etcd,armstrongli/etcd,glevand/coreos--etcd,bluebreezecf/etcd,a-robinson/etcd,plasticbox/etcd,bdarnell/etcd,heyitsanthony/etcd,li-ang/etcd,bluebreezecf/etcd,armstrongli/etcd,etcd-io/etcd,whuwxl/etcd,sinsharat/etcd,gyuho/etcd,mqliang/etcd,akauppi/etcd,fanminshi/etcd,li-ang/etcd,a-robinson/etcd,vimalk78/etcd,gyuho/etcd,joshix/etcd,akauppi/etcd,heyitsanthony/etcd,joshix/etcd,mkumatag/etcd,sinsharat/etcd,mqliang/etcd,tguangch/etcd,mickep76/etcd,vimalk78/etcd,whuwxl/etcd,sebrandon1/etcd,mkumatag/etcd,rnaveiras/etcd,dannysauer/etcd,ajityagaty/etcd,ajityagaty/etcd,rnaveiras/etcd,lorneli/etcd,cockroachdb/etcd,dannysauer/etcd,plasticbox/etcd,sebrandon1/etcd,visheshnp/etcd,etcd-io/etcd,visheshnp/etcd,etcd-io/etcd,mickep76/etcd,YuleiXiao/etcd,cockroachdb/etcd,yudai/etcd,YuleiXiao/etcd,bdarnell/etcd,ajityagaty/etcd,coreos/etcd,mqliang/etcd,fanminshi/etcd,lorneli/etcd,tguangch/etcd,xiang90/etcd,xiang90/etcd