clientv3/integration: use 'transport.IsClosedConnError'
clientv3/integration: use 'transport.IsClosedConnError'

Signed-off-by: Gyu-Ho Lee <3454051ee3341eb69bdf6fca40899cdad4d86496@gmail.com>

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