[CI] testing model not exists on crashdump step

[jneo8]

Found on: canonical/hardware-observer-operator#314

The model will be removed after functional test finish, no matter it's success or failed.
The issue is be found on the pytest-operator, we should also check zaza if the issue exists.

The solution for pytest-operator is to apply --keep-models on the arguments so the model will be keeped.

[samuelallan72]

@jneo8 I think the best place to fix this would be to add --keep-models to all the test_commands template variables in this repo. What do you think? Similar to this:

solutions-engineering-automation/terraform-plans/configs/hardware-observer-operator_main.tfvars

Line 21 in a97ec31

# test_commands = "['tox -e func -- -v --series focal --keep-models', 'tox -e func -- -v --series jammy --keep-models']",