* Fix issue#1874
Prior to this change, if user use one client connect emqx with mqtt
v3.1.1, the client subscribe the topic and publish message to this
topic, it would receive this message itself published, this commit
provide a configure option to let user ignore the message itself published.
This change fix issue 1874.
* Small Fix
* Fix bug
* Better design
* Fix compile warning and improve coverage
* Better design to solve the performance issue
* Fix typo
* Fix typo
* Delete spaces in end of lines.
* Do not use anonymous function
* Better performance
turtled