[BUG] Clear-cookie path issue

[BUG] Clear-cookie path issue

We have been using haproxy to balance a not very well written application
(http://www.blackboard.com/). Using the "insert postonly indirect" cookie
method, I was attempting to remove the cookie when users would logout,
allowing the machine to re-balance for the next user (this application is
used in school computer labs, so a computer might stay on the whole day
but be used on and off).

I was having a lot of trouble because when the cookie was set, it was with
"Path=/", but when being cleared there was no "Path" in the set cookie
header, and because the logout page was in a different place of the
website (which I couldn't change), the cookie would not be cleared. I
don't know if this would be a problem for anyone other than me (as our
HTTP application is so un-adjustable), but just in case, I have included
the patch I used. Maybe it will help someone else.

[ WT: this was a correct fix, and I also added the same missing path to
  the set-cookie option ]