Unauthorized for K8s API during charm removal

[Kenneth Koski]

An example charm that reproduces the issue:

```
import os
import subprocess

import requests
from ops.charm import CharmBase
from ops.main import main
from ops.model import ActiveStatus

class Operator(CharmBase):
    def __init__(self, *args):
        super().__init__(*args)
        self.framework.observe(self.on.foo_pebble_ready, self.install)
        self.framework.observe(self.on.remove, self.remove)

    def install(self, event):
        response = requests.get('https://dl.k8s.io/release/v1.22.1/bin/linux/amd64/kubectl')
        response.raise_for_status()

        with open('/bin/kubectl', 'wb') as f:
            f.write(response.content)

        os.chmod("/bin/kubectl", 0o755)

        subprocess.check_call(["kubectl", "get", "pods"])
        self.unit.status = ActiveStatus()

    def remove(self, event):
        subprocess.check_call(["kubectl", "get", "pods"])

if __name__ == "__main__":
    main(Operator)
```

Charm deployment works without an issue. However, when removing the charm, I get this error:

```
unit-foo-0: 16:00:00 WARNING unit.foo/0.remove error: You must be logged in to the server (Unauthorized)
unit-foo-0: 16:00:00 ERROR unit.foo/0.juju-log Uncaught exception while in charm code:
Traceback (most recent call last):
  File "/var/lib/juju/agents/unit-foo-0/charm/./src/charm.py", line 85, in <module>
    main(Operator)
  File "/var/lib/juju/agents/unit-foo-0/charm/venv/ops/main.py", line 406, in main
    _emit_charm_event(charm, dispatcher.event_name)
  File "/var/lib/juju/agents/unit-foo-0/charm/venv/ops/main.py", line 140, in _emit_charm_event
    event_to_emit.emit(*args, **kwargs)
  File "/var/lib/juju/agents/unit-foo-0/charm/venv/ops/framework.py", line 278, in emit
    framework._emit(event)
  File "/var/lib/juju/agents/unit-foo-0/charm/venv/ops/framework.py", line 722, in _emit
    self._reemit(event_path)
  File "/var/lib/juju/agents/unit-foo-0/charm/venv/ops/framework.py", line 767, in _reemit
    custom_handler(event)
  File "/var/lib/juju/agents/unit-foo-0/charm/./src/charm.py", line 57, in remove
    subprocess.check_call(["kubectl", "get", "pods"])
  File "/usr/lib/python3.9/subprocess.py", line 373, in check_call
    raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '['kubectl', 'get', 'pods']' returned non-zero exit status 1.
```

[Guillaume Belanger (gruyaume)]

This bug also affects charmed-magma (https://github.com/canonical/charmed-magma). We need to do manual cleanups of k8s resources created by charms because of it.

[Harry Pidcock (hpidcock)]

https://github.com/juju/juju/pull/13816