Modified judgement for time between posts.

Created function `shortDelayTime` in `/api/jiekouapi.php` to judge the time between two posts. The function has been used in 3 places in the code. 
This is the bug! You shouldn't `exit` if the post is fine!
Just remove this line and everything should be fine.
But this is my mistake, seems I have tested a wrong version.
Plz fix this in a new pull request.