* server: fix LRU hang on multiple requests same model
* server: keep a queued model out of the victim pool until its waiters leave
A waiter that gave up while its model was still loading left the
model idle with no request behind it, and nothing recounted the free
slots, so a second request queued behind it stayed queued forever.
tick() was only driven by requests: join, claim and the end of a
proxied request.
Keep the queue entry alive after a successful claim so the model
coming up is never picked as a victim before its waiters use it, and
recount the slots on every status change and whenever a waiter
abandons the queue. The model is then evicted as soon as it comes up
with nobody left to serve.
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Co-authored-by: Pascal <admin@serveurperso.com>
