[ISSUE #96] resolve the placeholder for "listener.txProducerGroup()"

[brucevoin]

What is the purpose of the change

#96 resolve the placeholder for "listener.txProducerGroup()"

Brief changelog

resolve the placeholder for "listener.txProducerGroup()" in file RocketMQTransactionAnnotationProcessor.java

Verifying this change

when add TransactionListener like this :

@RocketMQTransactionListener(txProducerGroup = "${demo.rocketmq.transaction.producer.group}")
class TransactionListenerImpl implements RocketMQLocalTransactionListener {
    private static final Logger LOGGER = LoggerFactory.getLogger(TransactionListenerImpl.class);

    private AtomicInteger transactionIndex = new AtomicInteger(0);

    private ConcurrentHashMap<String, Integer> localTrans = new ConcurrentHashMap<>();

the txProducerGroup can be injected from configuation like application.properties file.

[vongosling]

@fenghaichun Could you add some test for the pr?

[brucevoin]

@fenghaichun Could you add some test for the pr?

I have added the unit test for this PR, please check it out for me, thank you very much.

[brucevoin]

@vongosling The CI have failed, and it says "jdk_switcher: command not found", i don't know how to resolve it, can you help me to check this problem?

[vongosling]

@fenghaichun Thanks. Travis moved forward to be not compatible with the old configuration. we will fix it after merging your pr.

[vongosling]

@fenghaichun #109