[core][distributed] fix zmq hang (#6759)

[russellb]

(cherry picked from commit 740374d)

The ideal fix here is to upgrade to at least v0.5.4. In case that turns out to be not practical for some reason, I wanted to stage this backport for inclusion in the instructlab branch.

https://issues.redhat.com/browse/RHELAI-1211

[github-actions]

👋 Hi! Thank you for contributing to the vLLM project.
Just a reminder: PRs would not trigger full CI run by default. Instead, it would only trigger fastcheck CI to run, which consists only a small and essential subset of tests to quickly catch errors with the flexibility to run extra individual tests on top (you can do this by unblocking test steps in the Buildkite run).

Full CI run is still required to merge this PR so once the PR is ready to go, please make sure to run it. If you need all test signals in between PR commits, you can trigger full CI as well.

To run full CI, you can do one of these:

• Comment /ready on the PR
• Add ready label to the PR
• Enable auto-merge.

🚀

[n1hility]

/lgtm

[n1hility]

/approve

[openshift-ci]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: dtrifiro, n1hility, russellb

The full list of commands accepted by this bot can be found here.

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment