BLK-179 Rest polling only resets the recent posts for the current query

Signed-off-by: Oren Leiman <oleiman@neutral.io>
The default behavior of _get_post_id() is to return None. This should result in special behavior where the post is not considered a duplicate. I'm having a hard time reading this loop here and figuring out what would happen. It looks like the first None would get added to _recent_posts and then the next ones would be considered duplicates. Can you double check this please?