[Provisioner] make azure state check more robust

[Michaelvll]

A user reported that when launching a spot Azure VM, it is possible that a state code does not contain / which causes the following error:

  File "/home/azureuser/miniconda3/lib/python3.10/site-packages/sky/skylet/providers/azure/node_provider.py", line 105, in <listcomp>
    nodes = [self._extract_metadata(vm) for vm in filter(match_tags, vms)]
  File "/home/azureuser/miniconda3/lib/python3.10/site-packages/sky/skylet/providers/azure/node_provider.py", line 119, in _extract_metadata
    code, state = status["code"].split("/")
ValueError: too many values to unpack (expected 2)

We now add a handling for this special case.

Tested (run the relevant ones):

• Code formatting: bash format.sh
• Any manual or new tests for this PR (please specify below)
• 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: bash tests/backward_comaptibility_tests.sh

[cblmemo]

Thanks for fixing this! LGTM.