support passing additional env vars to host

[rplevka]

addresses:
#174

These commits add support for additional env vars. the following approaches work:

nick:

my_nick:
  container_host: "ubi8:rplevka"
  environment:
    ARG1: "val1"
    ARG2: "val2"

cli:

broker checkout --nick my_nick --environment "ARG1=val1,ARG2=val2"

Also, the processing of the args_file was refactored to combine parsed args with eventual cli args (cli args taking precedence)

[ogajduse]

There is one unit test failing: https://github.com/SatelliteQE/broker/actions/runs/3707727860/jobs/6284488033

[rplevka]

There is one unit test failing: https://github.com/SatelliteQE/broker/actions/runs/3707727860/jobs/6284488033

Odd, It is passing on my local, python 3.9 env setup:

$ pytest tests/ --ignore tests/functional
================================ test session starts ================================
platform linux -- Python 3.9.12, pytest-7.2.0, pluggy-1.0.0 -- /home/rplevka/.virtualenvs/broker/bin/python
cachedir: .pytest_cache
rootdir: /home/rplevka/work/rplevka/broker, configfile: pytest.ini
collected 32 items                                                                  

tests/test_broker.py::test_empty_init PASSED                                  [  3%]
tests/test_broker.py::test_kwarg_assignment PASSED                            [  6%]
tests/test_broker.py::test_full_init PASSED                                   [  9%]
tests/test_broker.py::test_broker_e2e PASSED                                  [ 12%]
tests/test_broker.py::test_broker_empty_checkin PASSED                        [ 15%]
tests/test_broker.py::test_mp_checkout PASSED                                 [ 18%]
tests/test_broker.py::test_mp_checkout_twice PASSED                           [ 21%]
tests/test_broker.py::test_mp_decorator PASSED                                [ 25%]
tests/test_helpers.py::test_load_json_file PASSED                             [ 28%]
tests/test_helpers.py::test_load_yaml_file PASSED                             [ 31%]
tests/test_helpers.py::test_negative_load_file PASSED                         [ 34%]
tests/test_helpers.py::test_resolve_file_args PASSED                          [ 37%]
tests/test_helpers.py::test_emitter PASSED                                    [ 40%]
tests/test_helpers.py::test_lock_file_created PASSED                          [ 43%]
tests/test_helpers.py::test_lock_timeout PASSED                               [ 46%]
tests/test_helpers.py::test_find_origin_simple PASSED                         [ 50%]
tests/test_helpers.py::test_find_origin_fixture PASSED                        [ 53%]
tests/test_helpers.py::test_find_origin_jenkins[set_envars0] PASSED           [ 56%]
tests/test_helpers.py::test_flatten_duplicate PASSED                          [ 59%]
tests/test_settings.py::test_default_settings PASSED                          [ 62%]
tests/test_settings.py::test_alternate_settings PASSED                        [ 65%]
tests/test_settings.py::test_validator_trigger PASSED                         [ 68%]
tests/test_settings.py::test_nested_envar[set_envars0] PASSED                 [ 71%]
tests/test_settings.py::test_default_envar[set_envars0] PASSED                [ 75%]
tests/test_settings.py::test_nondefault_envar[set_envars0] PASSED             [ 78%]
tests/test_settings.py::test_purge_vault_envars[set_envars0] PASSED           [ 81%]
tests/providers/test_ansible_tower.py::test_execute PASSED                    [ 84%]
tests/providers/test_ansible_tower.py::test_host_creation PASSED              [ 87%]
tests/providers/test_ansible_tower.py::test_workflow_lookup_failure PASSED    [ 90%]
tests/providers/test_container.py::test_empty_init PASSED                     [ 93%]
tests/providers/test_container.py::test_host_creation PASSED                  [ 96%]
tests/providers/test_container.py::test_image_lookup_failure PASSED           [100%]

================================ 32 passed in 9.99s =================================