server : do not clear slots without unified KV cache (#24190)
* Always export idle slots to RAM
Without this, a slot's VRAM cache may not be written to RAM. If this
slot happens to be busy then later on, this triggers needless
preprocessing in another slot.
* cont : clean-up
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Co-authored-by: Christoph Weiss <weiss@wsoptics.de>
Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>
