### What this PR does / why we need it?
The community has added a cleaning mechanism for the metadata after the
main model finishes running. The MTP layer should not clean the
metadata, and a new condition has been added to avoid cleaning it.
### Does this PR introduce _any_ user-facing change?
No
### How was this patch tested?
By ci
- vLLM version: v0.16.0
- vLLM main:
4034c3d32e
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Signed-off-by: wangxiaoteng <wangxiaoteng@huawei.com>