[Flaky-test]: Fix MLTransactionMetadataStoreTest.testInitTransactionReader fails sporadically
### Motivation
When update states is `TxnStatus.COMMITTED`,  Not correctly `completableFuture.complete`.
### Modifications
When update states is `TxnStatus.COMMITTED`, Add return to ending. Avoid direct calls `completableFuture.complete` from other logic.
### Documentation
[x ] `no-need-doc`
@@ -393,6 +393,7 @@ public class MLTransactionMetadataStore
txnMetaMap.remove(txnID.getLeastSigBits());
completableFuture.complete(null);
});
+ return;
}
completableFuture.complete(null);
} catch (InvalidTxnStatusException e) {
