Disable checkpoint/restore unit tests for docker

Currently, nerdctl CI uses docker 28.0.4, while docker version 28.x
has a known regression that breaks Checkpoint/Restore functionality.
The issue is tracked in the moby/moby project as moby/moby#50750.

Signed-off-by: ChengyuZhu6 <hudson@cyzhu.com>

Author: ChengyuZhu6

cmd/nerdctl/checkpoint/checkpoint_create_linux_test.go

@@ -30,7 +30,11 @@ import (
 
 func TestCheckpointCreateErrors(t *testing.T) {
 	testCase := nerdtest.Setup()
+
 	testCase.Require = require.Not(nerdtest.Rootless)
+	// Docker version 28.x has a known regression that breaks Checkpoint/Restore functionality.
+	// The issue is tracked in the moby/moby project as https://github.com/moby/moby/issues/50750.
+	testCase.Require = require.Not(nerdtest.Docker)
 	testCase.SubTests = []*test.Case{
 		{
 			Description: "too-few-arguments",
@@ -72,6 +76,9 @@ func TestCheckpointCreate(t *testing.T) {
 	)
 	testCase := nerdtest.Setup()
 	testCase.Require = require.Not(nerdtest.Rootless)
+	// Docker version 28.x has a known regression that breaks Checkpoint/Restore functionality.
+	// The issue is tracked in the moby/moby project as https://github.com/moby/moby/issues/50750.
+	testCase.Require = require.Not(nerdtest.Docker)
 	testCase.SubTests = []*test.Case{
 		{
 			Description: "leave-running=true",

cmd/nerdctl/container/container_start_linux_test.go

@@ -86,6 +86,9 @@ func TestStartWithCheckpoint(t *testing.T) {
 	testCase := nerdtest.Setup()
 	testCase.Require = require.Not(nerdtest.Rootless)
 
+	// Docker version 28.x has a known regression that breaks Checkpoint/Restore functionality.
+	// The issue is tracked in the moby/moby project as https://github.com/moby/moby/issues/50750.
+	testCase.Require = require.Not(nerdtest.Docker)
 	testCase.Setup = func(data test.Data, helpers test.Helpers) {
 		// Start a workload with verifiable state: record continuously increment /tmp/counter
 		helpers.Ensure("run", "-d", "--name", data.Identifier(), testutil.CommonImage,