tox: pass PYCLOUDLIB_* env vars into integration tests when present

[blackboxsw]

Proposed Commit Message

tox: pass PYCLOUDLIB_* env vars into integration tests when present

Allow any PYCLOUDLIB_* environment variables in integration-tests and jenkins
environments to allow overriding default behavior.

This specifically helps jenkins which seeds PYCLOUDLIB_CONFIG env var for
secrets.

Additional Context

Test Steps

# running the tox command before you create this file will result in errors like:
#   >       raise ValueError(
            "No configuration file found! Copy pycloudlib.toml.template to "
            "~/.config/pycloudlib.toml or /etc/pycloudlib.toml"
        )


cat > /tmp/test.toml <<EOF
[lxd]
EOF

CLOUD_INIT_PLATFORM=lxd_vm CLOUD_INIT_OS_IMAGE=jammy CLOUD_INIT_CLOUD_INIT_SOURCE=ppa:cloud-init-dev/daily CLOUD_INIT_COLLECT_LOGS=ON_ERROR PYCLOUDLIB_CONFIG=/tmp/test.toml  tox -e  integration-tests tests/integration_tests/modules/test_cli.py

Checklist:

• My code follows the process laid out in the documentation
• I have updated or added any unit tests accordingly
• I have updated or added any documentation accordingly

[blackboxsw]

related jenkins build failure showing that PYCLOUDLIB_CONFIG env var isn't being honored/seen https://jenkins.ubuntu.com/server/view/cloud-init/job/cloud-init-integration-lxd_vm-jammy-daily/12/consoleFull

[TheRealFalcon]

Thanks!