integration: cancel operation for unsynced watcher
integration: cancel operation for unsynced watcher

Related https://github.com/coreos/etcd/issues/4216.

lumjjb/etcd,whuwxl/etcd,YuleiXiao/etcd,hongchaodeng/etcd,purpleidea/etcd,linuxcer/etcd,xiang90/etcd,handsomesun/etcd,akauppi/etcd,rnaveiras/etcd,jlamillan/etcd,purpleidea/etcd,CrazyJvm/etcd,nekto0n/etcd,xiang90/etcd,chipironcin/etcd,ajityagaty/etcd,westhood/etcd,sinsharat/etcd,sofuture/etcd,etcd-io/etcd,tamird/etcd,li-ang/etcd,StorReduce/etcd,nekto0n/etcd,zaphod-concur/etcd,akauppi/etcd,dnaeon/etcd,siddontang/etcd,yudai/etcd,mkumatag/etcd,lumjjb/etcd,visheshnp/etcd,OyTao/etcd_learning,cockroachdb/etcd,ktateish/etcd,mickep76/etcd,joshix/etcd,lorneli/etcd,hongchaodeng/etcd,luxas/etcd,vimalk78/etcd,mickep76/etcd,wantonsolutions/dinv-etcd,ktateish/etcd,jonboulle/etcd,CrazyJvm/etcd,ravigadde/etcd,bluebreezecf/etcd,endocode/etcd,OyTao/etcd_learning,mkumatag/etcd,wantonsolutions/dinv-etcd,handsomesun/etcd,tguangch/etcd,cockroachdb/etcd,YuleiXiao/etcd,ajityagaty/etcd,swingbach/etcd,swingbach/etcd,rchicoli/etcd,raoofm/etcd,coreos/etcd,achanda/etcd,sebrandon1/etcd,qqsun8819/etcd,plasticbox/etcd,glevand/coreos--etcd,jonboulle/etcd,glycerine/etcd,yudai/etcd,coreos/etcd,dnaeon/etcd,bdarnell/etcd,raoofm/etcd,insequent/etcd,mqliang/etcd,armstrongli/etcd,ravigadde/etcd,glycerine/etcd,joshix/etcd,shawnps/etcd,linuxcer/etcd,sofuture/etcd,rnaveiras/etcd,gyuho/etcd,qqsun8819/etcd,rnaveiras/etcd,plasticbox/etcd,siddontang/etcd,tguangch/etcd,wantonsolutions/dinv-etcd,zaphod-concur/etcd,StorReduce/etcd,heyitsanthony/etcd,shawnps/etcd,ajityagaty/etcd,westhood/etcd,bluebreezecf/etcd,etcd-io/etcd,armstrongli/etcd,achanda/etcd,bdarnell/etcd,mqliang/etcd,mqliang/etcd,jlamillan/etcd,vimalk78/etcd,sinsharat/etcd,visheshnp/etcd,fanminshi/etcd,lorneli/etcd,mkumatag/etcd,a-robinson/etcd,heyitsanthony/etcd,dannysauer/etcd,fanminshi/etcd,etcd-io/etcd,luxas/etcd,a-robinson/etcd,sebrandon1/etcd,whuwxl/etcd,tamird/etcd,rchicoli/etcd,dannysauer/etcd,li-ang/etcd,endocode/etcd,chipironcin/etcd,insequent/etcd,gyuho/etcd,glevand/coreos--etcd