Forums new post form should reset state when user cancels

TNL-148
I'm ok with "Your post will be discarded." or "The post will be discarded." and letting the button labels speak for themselves @gwprice ? @talbs ?
(Background of my thinking for those who have time and interest follows)
1. message boxes should provide a clear path of action. Having clicked Cancel, seeing "Are you sure you want to cancel?" with choices of Ok and Cancel may not fit the bill. 2. one tries to craft a message with a positive construction rather than a negative construction 3. one tries to think in terms of translation, so "discard" or "delete" are likely to be clearer than "lost" 4. the "are you sure" construction is often seen as both patronizing and a waste of time as it does not itself provide information, causing many people to skip the entire message and miss the useful info in the 2nd sentence.