clients/tests: add python test script for nmcli tests
Add a test which runs nmcli against our stub NetworkManager service and compares the output. The output formats of nmcli are complicated and not easily understood. For example how --mode tabular|multiline interacts with selecting output-fields (--fields) and output modes ([default]|--terse|--pretty). Also, there are things like `nmcli connection show --order $FIELD_SPEC`. We need unit tests to ensure that we don't change the output accidentally.
Showing with 1520 additions and 76 deletions