functional-tester/tester: update import paths

Signed-off-by: Gyuho Lee <gyuhox@gmail.com>

tools/functional-tester/tester/cluster.go

@@ -27,10 +27,10 @@ import (
 	pb "github.com/coreos/etcd/etcdserver/etcdserverpb"
 	"github.com/coreos/etcd/pkg/debugutil"
 	"github.com/coreos/etcd/tools/functional-tester/rpcpb"
-	"golang.org/x/time/rate"
 
 	"github.com/prometheus/client_golang/prometheus/promhttp"
 	"go.uber.org/zap"
+	"golang.org/x/time/rate"
 	"google.golang.org/grpc"
 	yaml "gopkg.in/yaml.v2"
 )