### What this PR does / why we need it?
- skip the nightly image build when the github event is pull_request
- set imagepullpolicy as alway for multi_node test
- move multi_node tests ahead to have some resource clean first
- do not relevant nightly image build with nightly tests for tolerance
- vLLM version: v0.11.0
- vLLM main:
2918c1b49c
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Signed-off-by: hfadzxy <starmoon_zhang@163.com>
Signed-off-by: wangli <wangli858794774@gmail.com>
Co-authored-by: wangli <wangli858794774@gmail.com>