Reaper and Azure not playing nice together

It appears that reaper is trying to remove instances that no longer exist.

Locally, I have seen this:
```
2025-02-25 11:20:06 INFO integration_testing:conftest.py:505 finishing session
2025-02-25 11:20:06 INFO integration_testing:clouds.py:196 Deleting snapshot image created for this testrun: /subscriptions/36c65514-b88a-44f1-a44a-795c5b6fb73c/resourceGroups/azure-integration-test-0225-111550-rg/providers/Microsoft.Compute/images/azure-integration-test-0225-111551-image
Exception in thread reaper:
Traceback (most recent call last):
File "/home/james/.pyenv/versions/3.8.16/lib/python3.8/threading.py", line 932, in _bootstrap_inner
self.run()
File "/home/james/.pyenv/versions/3.8.16/lib/python3.8/threading.py", line 870, in run
self._target(*self._args, **self._kwargs)
File "/home/james/c/cloud-init/tests/integration_tests/reaper.py", line 120, in _reaper_loop
if self._do_reap():
File "/home/james/c/cloud-init/tests/integration_tests/reaper.py", line 144, in _do_reap
LOG.info("Reaper: destroyed %s", instance.instance.id)
File "/home/james/c/pycloudlib/pycloudlib/azure/instance.py", line 116, in id
return self._instance["vm"].id
TypeError: 'NoneType' object is not subscriptable
2025-02-25 11:20:37 INFO root:reaper.py:82 Reaper: stopping
2025-02-25 11:20:37 INFO root:reaper.py:86 Reaper: awakened to reap
2025-02-25 11:20:37 INFO root:reaper.py:89 Reaper: stopped
2025-02-25 11:21:53 INFO integration_testing:conftest.py:535 finish session
```
and in [Jenkins](https://jenkins.canonical.com/server-team/view/cloud-init/job/cloud-init-integration-focal-azure-generic/566/consoleText), I'm seeing:
```
[2025-02-20T03:22:25.847Z] tests/integration_tests/bugs/test_gh671.py::test_update_default_password
[2025-02-20T03:22:25.847Z] /jenkins/servers/serverteam/workspace/cloud-init-integration-focal-azure-generic/cloud-init-99.daily-202502190032/.tox/integration-tests-jenkins/lib/python3.10/site-packages/_pytest/threadexception.py:82: PytestUnhandledThreadExceptionWarning: Exception in thread reaper
[2025-02-20T03:22:25.847Z]
[2025-02-20T03:22:25.847Z] Traceback (most recent call last):
[2025-02-20T03:22:25.847Z] File "/usr/lib/python3.10/threading.py", line 1016, in _bootstrap_inner
[2025-02-20T03:22:25.847Z] self.run()
[2025-02-20T03:22:25.847Z] File "/usr/lib/python3.10/threading.py", line 953, in run
[2025-02-20T03:22:25.847Z] self._target(*self._args, **self._kwargs)
[2025-02-20T03:22:25.847Z] File "/jenkins/servers/serverteam/workspace/cloud-init-integration-focal-azure-generic/cloud-init-99.daily-202502190032/tests/integration_tests/reaper.py", line 120, in _reaper_loop
[2025-02-20T03:22:25.847Z] if self._do_reap():
[2025-02-20T03:22:25.847Z] File "/jenkins/servers/serverteam/workspace/cloud-init-integration-focal-azure-generic/cloud-init-99.daily-202502190032/tests/integration_tests/reaper.py", line 144, in _do_reap
[2025-02-20T03:22:25.847Z] LOG.info("Reaper: destroyed %s", instance.instance.id)
[2025-02-20T03:22:25.847Z] File "/jenkins/servers/serverteam/workspace/cloud-init-integration-focal-azure-generic/cloud-init-99.daily-202502190032/.tox/integration-tests-jenkins/lib/python3.10/site-packages/pycloudlib/azure/instance.py", line 116, in id
[2025-02-20T03:22:25.847Z] return self._instance["vm"].id
[2025-02-20T03:22:25.847Z] TypeError: 'NoneType' object is not subscriptable
[2025-02-20T03:22:25.847Z]
[2025-02-20T03:22:25.847Z] warnings.warn(pytest.PytestUnhandledThreadExceptionWarning(msg))
```