### What this PR does / why we need it?
The previous implementation of the flashcomm2 communication domain did
not consider pp(pipeline parallel), which caused problems when enabling
pp and flashcomm2. This PR fixes this issue.
- vLLM version: v0.11.2
- vLLM main: https://github.com/vllm-project/vllm/commit/v0.11.2
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Signed-off-by: zzhx1 <zzh_201018@outlook.com>
Co-authored-by: Levi-JQ <yujinqi2@huawei.com>
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