[arena] displays way more kills than are possible

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* What steps will reproduce the problem?
Join an arena server _after the first match_, and after the server has gone 
through several maps.
Hold tab to see kills.

* What is the expected output? What do you see instead?
Expect to see the usual kill count for players. Max around 100.

Instead, I see a ton of crazy high kill counts. 15 people with > 150 kills, 
which is not even possible in arena.

* Revision
Current aloha.pk server.

* Additional Info
This is probably a side effect of how kill counts aren't cleared internally 
between map changes.

Original issue reported on code.google.com by [email protected] on 15 Jul 2012 at 4:37