lease: acquire BatchTx lock in fakeDeleter

Revoke expects the BatchTx lock to be held when holding the TxnDeleter
because it updates the lease bucket. The tests don't hold the lock so
it may race with the backend commit loop.

Fixes #7662

lease/lessor_test.go

@@ -87,7 +87,7 @@ func TestLeaseConcurrentKeys(t *testing.T) {
 	defer be.Close()
 
 	le := newLessor(be, minLeaseTTL)
-	le.SetRangeDeleter(func() TxnDelete { return &fakeDeleter{} })
+	le.SetRangeDeleter(func() TxnDelete { return newFakeDeleter(be) })
 
 	// grant a lease with long term (100 seconds) to
 	// avoid early termination during the test.
@@ -133,10 +133,12 @@ func TestLessorRevoke(t *testing.T) {
 	defer os.RemoveAll(dir)
 	defer be.Close()
 
-	fd := &fakeDeleter{}
-
 	le := newLessor(be, minLeaseTTL)
-	le.SetRangeDeleter(func() TxnDelete { return fd })
+	var fd *fakeDeleter
+	le.SetRangeDeleter(func() TxnDelete {
+		fd = newFakeDeleter(be)
+		return fd
+	})
 
 	// grant a lease with long term (100 seconds) to
 	// avoid early termination during the test.
@@ -214,7 +216,7 @@ func TestLessorDetach(t *testing.T) {
 	defer be.Close()
 
 	le := newLessor(be, minLeaseTTL)
-	le.SetRangeDeleter(func() TxnDelete { return &fakeDeleter{} })
+	le.SetRangeDeleter(func() TxnDelete { return newFakeDeleter(be) })
 
 	// grant a lease with long term (100 seconds) to
 	// avoid early termination during the test.
@@ -376,9 +378,16 @@ func TestLessorExpireAndDemote(t *testing.T) {
 
 type fakeDeleter struct {
 	deleted []string
+	tx      backend.BatchTx
+}
+
+func newFakeDeleter(be backend.Backend) *fakeDeleter {
+	fd := &fakeDeleter{nil, be.BatchTx()}
+	fd.tx.Lock()
+	return fd
 }
 
-func (fd *fakeDeleter) End() {}
+func (fd *fakeDeleter) End() { fd.tx.Unlock() }
 
 func (fd *fakeDeleter) DeleteRange(key, end []byte) (int64, int64) {
 	fd.deleted = append(fd.deleted, string(key)+"_"+string(end))