### What this PR does / why we need it?
Synchronize the host query_start_loc with device values to prevent shape
mismatches when not enable async scheduling.
### Does this PR introduce _any_ user-facing change?
None.
### How was this patch tested?
None.
- vLLM version: v0.12.0
- vLLM main:
ad32e3e19c
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Signed-off-by: Yizhou Liu <liu_yizhou@outlook.com>