`az container exec` fails with 'certificate verify failed'

### **This is autogenerated. Please review and update as needed.**

## Describe the bug

**Command Name**
`az container exec`

**Errors:**
```
[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:852)
Traceback (most recent call last):
python3.6/site-packages/knack/cli.py, ln 215, in invoke
cmd_result = self.invocation.execute(args)
cli/core/commands/__init__.py, ln 654, in execute
raise ex
cli/core/commands/__init__.py, ln 718, in _run_jobs_serially
results.append(self._run_job(expanded_arg, cmd_copy))
cli/core/commands/__init__.py, ln 711, in _run_job
six.reraise(*sys.exc_info())
...
az/lib/python3.6/ssl.py, ln 817, in __init__
self.do_handshake()
az/lib/python3.6/ssl.py, ln 1077, in do_handshake
self._sslobj.do_handshake()
az/lib/python3.6/ssl.py, ln 689, in do_handshake
self._sslobj.do_handshake()
ssl.SSLError: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:852)
```

## To Reproduce:
Steps to reproduce the behavior. Note that argument values have been redacted, as they may contain sensitive information.

- _Put any pre-requisite steps here..._
- `az container exec --resource-group {} --name {} --exec-command {}`

## Expected Behavior

## Environment Summary
```
Linux-4.15.0-1093-azure-x86_64-with-debian-stretch-sid (Cloud Shell)
Python 3.6.10
Installer: DEB

azure-cli 2.11.1

Extensions:
ai-examples 0.2.3

```
## Additional Context

Start with the reported `az container exec --resource-group {} --name {} --exec-command {}` command in the listed Cloud Shell environment, then trace the failure through `knack/cli.py` and the Python `ssl.py` handshake shown in the traceback. Done means the command completes without the certificate verification error, with a regression check for the reported environment.

Written by the indexing model from the issue text.