Do not mark post unread for any action other than creation

Currently a post is marked back to unread on any action.

Requirements:
Do not mark a post unread for these actions:

• follow

• endorse

• mark as answer

• vote

• edit

• delete

• report

Dev Detail:
We keep track of 'read' status based on thread update date and 'read' date. Hence, implicitly mark a post read on any of above actions.