Fix PUA module so that it sends a final PUBLISH on expiration.

[dsandras]

A final PUBLISH with expires=0 is now generated when a publication
has expired. This will trigger the transmission of a final state NOTIFY.

If accepted, please credit Damien Sandras from Be IP s.a. @ http://www.beip.be

[dsandras]

From my point of view, the correct fix is to:

1. Send a final PUBLISH
2. Delete the item from the hash table
   I have double checked all of this and can confirm my pull request works as it should.

[saghul]

LGTM, can you please squash the commits into one?

[dsandras]

Sure. I'll do it before the end of the day and generate a new pull request.

[saghul]

Great! No need to create a new one, just force push (push -f) to the branch where you made the request from.

[dsandras]

I think it is now like you want it :)

Damien

[saghul]

Yep, thanks! I'll try to merge it later today, first on master and then backport it down to 1.8 (can you confirm, @bogdan-iancu ?). Hopefully there are no conflicts :-)

[saghul]

Thanks, Damien! It landed on c5a57a8, 763ea32, f986bac and c2202a0

[dsandras]

Thanks !