Fix `rollbackEtcdData()` to return error=nil on success `rollbackEtcdData()` used to always return an error making the rest of the upgrade code completely unreachable. Ignore errors from `rollbackOldManifests()` during the rollback since it always returns an error. Success of the rollback is gated with etcd L7 healthchecks. Remove logic implying the etcd manifest should be rolled back when `upgradeComponent()` fails