### What this PR does / why we need it?
This PR add the always_check_nodes parameter to the
_wait_for_multiple_servers function in conftest.py for the EPD test
case.
### Does this PR introduce _any_ user-facing change?
no
### How was this patch tested?
1.by running the test
`pytest -sv test_disaggregated_encoder.py`
2.by running ci
- vLLM version: v0.17.0
- vLLM main:
4497431df6
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Signed-off-by: yenuo26 <410167048@qq.com>