server: reset counter related to kill-switch on client error (#20513)

server: reset counter related to kill-switch on client error (#20513)

* server: reset kill-switch on client error

This avoids triggering a server kill switch.

If the client sends a request that exceeds the configured context size, an appropriate HTTP 400 response is provided and no tokens are generated.

However since no tokens are generated, update_slots() increments n_empty_consecutive. If the client sends 3 such messages in a row, the server terminates.

* moved counter reset as per recommendation

* cont : minor

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Co-authored-by: Georgi Gerganov <redacted>