### What this PR does / why we need it?
The speculative inference acceptance rate decreases after the vllm
version is upgraded to v0.15.0. This issue is resolved.
### Does this PR introduce _any_ user-facing change?
no
### How was this patch tested?
UT and tests case
- vLLM version: v0.15.0
- vLLM main:
d7e17aaacd
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Signed-off-by: lilinsiman <lilinsiman@gmail.com>