[ISSUE #151] Fix the Infinite loop in DefaultRocketMQListenerContainer

[zhangjidi2016]

What is the purpose of the change

Fix the Infinite loop in DefaultRocketMQListenerContainer

Brief changelog

Adjust the getMessageType method

Verifying this change

XXXX

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[zongtanghu]

I suggest this pr can be merged after December 31.

[vongosling]

@zhangjidi2016 Great work, adding some related unit test for your pr could be convinced for a reviewer

[zhangjidi2016]

@zhangjidi2016 Great work, adding some related unit test for your pr could be convinced for a reviewer

OK，The DefaultRocketMQListenerContainerTest class has already existed the unit test for getMessageType method， and has passed the unit test after submit this PR.