Stop using math/rand.Read and rand.Seed (deprecated in Go 1.20)

From golangci-lint:

> SA1019: rand.Read has been deprecated since Go 1.20 because it
>shouldn't be used: For almost all use cases, crypto/rand.Read is more
>appropriate. (staticcheck)

> SA1019: rand.Seed has been deprecated since Go 1.20 and an alternative
>has been available since Go 1.0: Programs that call Seed and then expect
>a specific sequence of results from the global random source (using
>functions such as Int) can be broken when a dependency changes how
>much it consumes from the global random source. To avoid such breakages,
>programs that need a specific result sequence should use
>NewRand(NewSource(seed)) to obtain a random generator that other
>packages cannot access. (staticcheck)

See also:

- https://pkg.go.dev/math/rand@go1.20#Read
- https://pkg.go.dev/math/rand@go1.20#Seed

Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>

pkg/kmutex/kmutex_test.go

@@ -18,21 +18,16 @@ package kmutex
 
 import (
 	"context"
-	"math/rand"
 	"runtime"
 	"strconv"
 	"sync"
 	"testing"
 	"time"
 
-	"github.com/containerd/containerd/pkg/seed"
+	"github.com/containerd/containerd/pkg/randutil"
 	"github.com/stretchr/testify/assert"
 )
 
-func init() {
-	seed.WithTimeAndRand()
-}
-
 func TestBasic(t *testing.T) {
 	t.Parallel()
 
@@ -60,7 +55,7 @@ func TestBasic(t *testing.T) {
 				waitLock = true
 				break
 			}
-			time.Sleep(time.Duration(rand.Int63n(100)) * time.Millisecond)
+			time.Sleep(time.Duration(randutil.Int63n(100)) * time.Millisecond)
 		}
 		assert.Equal(t, waitLock, true)
 	}
@@ -130,7 +125,7 @@ func TestMultileAcquireOnKeys(t *testing.T) {
 			for i := 0; i < nloops; i++ {
 				km.Lock(ctx, key)
 
-				time.Sleep(time.Duration(rand.Int63n(100)) * time.Nanosecond)
+				time.Sleep(time.Duration(randutil.Int63n(100)) * time.Nanosecond)
 
 				km.Unlock(key)
 			}
@@ -161,7 +156,7 @@ func TestMultiAcquireOnSameKey(t *testing.T) {
 			for i := 0; i < nloops; i++ {
 				km.Lock(ctx, key)
 
-				time.Sleep(time.Duration(rand.Int63n(100)) * time.Nanosecond)
+				time.Sleep(time.Duration(randutil.Int63n(100)) * time.Nanosecond)
 
 				km.Unlock(key)
 			}