filer: etcd fix pagination

fix https://github.com/chrislusf/seaweedfs/issues/3016

weed/filer/etcd/etcd_store_test.go

@@ -0,0 +1,14 @@
+package etcd
+
+import (
+	"github.com/chrislusf/seaweedfs/weed/filer/store_test"
+	"testing"
+)
+
+func TestStore(t *testing.T) {
+	if false {
+		store := &EtcdStore{}
+		store.initialize("localhost:2379", "3s")
+		store_test.TestFilerStore(t, store)
+	}
+}