fix potential goroutine leaks in TestTxnPanics
fix potential goroutine leaks in TestTxnPanics

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