add code coverage (#615)

* add code coverage

* simplify redis code

core/stores/redis/redis.go

@@ -1742,17 +1742,9 @@ func acceptable(err error) bool {
 func getRedis(r *Redis) (RedisNode, error) {
 	switch r.Type {
 	case ClusterType:
-		if r.tls {
-			return getClusterWithTLS(r.Addr, r.Pass, r.tls)
-		} else {
-			return getCluster(r.Addr, r.Pass)
-		}
+		return getCluster(r)
 	case NodeType:
-		if r.tls {
-			return getClientWithTLS(r.Addr, r.Pass, r.tls)
-		} else {
-			return getClient(r.Addr, r.Pass)
-		}
+		return getClient(r)
 	default:
 		return nil, fmt.Errorf("redis type '%s' is not supported", r.Type)
 	}