tests: deflakey TestLeaseGrantTimeToLiveExpired

The following change can reproduce the issue #17504 by
`TESTCASE=TestLeaseGrantTimeToLiveExpired/PeerAutoTLS make test-e2e`. We
can retry it to reduce flakey possibility, if there is leader change.

```diff
diff --git a/tests/common/lease_test.go b/tests/common/lease_test.go
index afb27c330..dea8459dc 100644
--- a/tests/common/lease_test.go
+++ b/tests/common/lease_test.go
@@ -16,6 +16,7 @@ package common

 import (
        "context"
+       "sync"
        "testing"
        "time"

@@ -139,6 +140,18 @@ func TestLeaseGrantTimeToLiveExpired(t *testing.T) {
                                require.NoError(t, err)
                                require.Equal(t, int64(1), getResp.Count)

+                               var wg sync.WaitGroup
+                               defer wg.Wait()
+
+                               wg.Add(1)
+                               go func() {
+                                       defer wg.Done()
+                                       time.Sleep(1000 * time.Millisecond)
+                                       clus.(interface {
+                                               MoveLeader(ctx context.Context, t testing.TB, i int) error
+                                       }).MoveLeader(ctx, t, (clus.WaitLeader(t)+1)%len(clus.Members()))
+                               }()
+
                                time.Sleep(3 * time.Second)

                                ttlResp, err := cc.TimeToLive(ctx, leaseResp.ID, config.LeaseOption{})

```

Signed-off-by: Wei Fu <fuweid89@gmail.com>

tests/common/lease_test.go

@@ -122,7 +122,7 @@ func TestLeaseGrantTimeToLiveExpired(t *testing.T) {
 
 	for _, tc := range clusterTestCases() {
 		t.Run(tc.name, func(t *testing.T) {
-			ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+			ctx, cancel := context.WithTimeout(context.Background(), 15*time.Second)
 			defer cancel()
 			clus := testRunner.NewCluster(ctx, t, config.WithClusterConfig(tc.config))
 			defer clus.Close()
@@ -139,7 +139,23 @@ func TestLeaseGrantTimeToLiveExpired(t *testing.T) {
 				require.NoError(t, err)
 				require.Equal(t, int64(1), getResp.Count)
 
-				time.Sleep(3 * time.Second)
+				// FIXME: When leader changes, old leader steps
+				// back to follower and ignores the lease revoking.
+				// The new leader will restart TTL counting. If so,
+				// we should call time.Sleep again and wait for revoking.
+				// It can't avoid flakey but reduce flakey possiblility.
+				for i := 0; i < 3; i++ {
+					currentLeader := clus.WaitLeader(t)
+					t.Logf("[%d] current leader index %d", i, currentLeader)
+
+					time.Sleep(3 * time.Second)
+
+					newLeader := clus.WaitLeader(t)
+					if newLeader == currentLeader {
+						break
+					}
+					t.Logf("[%d] leader changed, new leader index %d", i, newLeader)
+				}
 
 				ttlResp, err := cc.TimeToLive(ctx, leaseResp.ID, config.LeaseOption{})
 				require.NoError(t, err)