update 3.4 change log for 3.4.19
update 3.4 change log for 3.4.19

mqliang/etcd,etcd-io/etcd,rnaveiras/etcd,ajityagaty/etcd,rnaveiras/etcd,etcd-io/etcd,ajityagaty/etcd,mqliang/etcd,ajityagaty/etcd,mkumatag/etcd,etcd-io/etcd,mqliang/etcd,mkumatag/etcd,mkumatag/etcd,rnaveiras/etcd