Removing state pollution of containers by making a deepcopy

[sturmianseq]

This PR aims to improve test reliability of test test_give_json by removing state pollution of containers by making a deepcopy.

The test can fail in this way by running pip3 install pytest-repeat; python3 -m pytest --count=2 tests/test_dockerprettyps.py::TestDockerPrettyPs::test_give_json:

    def test_give_json(self):
        """
        Tests the dockerprettyps.give_json() method, making sure we output the same data we would normally, but in JSON.
    
        """
        containers = copy.copy(test_ps_data.ps_containers)
>       the_json = dockerprettyps.give_json(containers, CliArgs())

tests/test_dockerprettyps.py:348: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

    def give_json(containers, args):
        ...
        clean_date_containers = _json_container_dates(containers)
        more_cleaned = []
        for container in clean_date_containers:
>           more_cleaned.append(container.pop('color'))
E           KeyError: 'color'

It may be better to clean state pollutions so that some other tests won't fail in the future due to the shared state pollution.