backup: deflake TestBackupRestoreChecksum under race

Fixes: cockroachdb#160062

Release note: None

Author: kev-cao

pkg/ccl/backupccl/backup_test.go

@@ -4088,6 +4088,11 @@ func TestBackupRestoreChecksum(t *testing.T) {
 	defer leaktest.AfterTest(t)()
 	defer log.Scope(t).Close(t)
 
+	// Test Server too slow under deadlock.
+	skip.UnderDeadlock(t)
+	// Flaky under race.
+	skip.UnderRace(t)
+
 	const numAccounts = 1000
 	_, sqlDB, dir, cleanupFn := backupRestoreTestSetup(t, singleNode, numAccounts, InitManualReplication)
 	defer cleanupFn()