[RunPod] Fix assertion in ports query.

[cblmemo]

Fixes #4286.

Tested (run the relevant ones):

• [ ] Code formatting: bash format.sh
• [x] Any manual or new tests for this PR (please specify below)
  • [x] sky serve up a service on runpod replica, and manually terminate it. all sky serve commands works properly and a restart is triggered.
• [ ] All smoke tests: pytest tests/test_smoke.py
• [ ] Relevant individual smoke tests: pytest tests/test_smoke.py::test_fill_in_the_name
• [ ] Backward compatibility tests: conda deactivate; bash -i tests/backward_compatibility_tests.sh