integration: use RequireLeader for TestV3LeaseFailover

Giving Renew() the default request timeout causes TestV3LeaseFailover
to miss its timing constraints. Since it only needs to wait until the
leader recognizes the leader is lost, use RequireLeader to cancel the
keepalive stream before the request times out.

integration/v3_lease_test.go

@@ -19,11 +19,13 @@ import (
 	"testing"
 	"time"
 
+	"golang.org/x/net/context"
+	"google.golang.org/grpc/metadata"
+
 	"github.com/coreos/etcd/etcdserver/api/v3rpc/rpctypes"
 	pb "github.com/coreos/etcd/etcdserver/etcdserverpb"
 	"github.com/coreos/etcd/mvcc/mvccpb"
 	"github.com/coreos/etcd/pkg/testutil"
-	"golang.org/x/net/context"
 )
 
 // TestV3LeasePrmote ensures the newly elected leader can promote itself
@@ -356,7 +358,9 @@ func TestV3LeaseFailover(t *testing.T) {
 
 	lreq := &pb.LeaseKeepAliveRequest{ID: lresp.ID}
 
-	ctx, cancel := context.WithCancel(context.Background())
+	md := metadata.Pairs(rpctypes.MetadataRequireLeaderKey, rpctypes.MetadataHasLeader)
+	mctx := metadata.NewContext(context.Background(), md)
+	ctx, cancel := context.WithCancel(mctx)
 	defer cancel()
 	lac, err := lc.LeaseKeepAlive(ctx)
 	if err != nil {