### What this PR does / why we need it?
When the draft model also uses vllmbackend for graph compilation, the
fusion pass registration occurs again, resulting in errors due to
duplicate patterns.
### Does this PR introduce _any_ user-facing change?
### How was this patch tested?
- vLLM version: v0.15.0
- vLLM main: https://github.com/vllm-project/vllm/commit/v0.15.0
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Signed-off-by: chencangtao <chencangtao@huawei.com>
Co-authored-by: chencangtao <chencangtao@huawei.com>