Fix the flaky test test_restart_tower_rollback (#23129)

* Add flag to disable voting until a slot to avoid duplicate voting

* Fix the tower rollback test and remove it from flaky.

local-cluster/src/validator_configs.rs

@@ -61,6 +61,7 @@ pub fn safe_clone_config(config: &ValidatorConfig) -> ValidatorConfig {
         no_wait_for_vote_to_start_leader: config.no_wait_for_vote_to_start_leader,
         accounts_shrink_ratio: config.accounts_shrink_ratio,
         accounts_db_config: config.accounts_db_config.clone(),
+        wait_to_vote_slot: config.wait_to_vote_slot,
     }
 }