Remove mistake-prone code

Consider how weird it is that these two calls are equivalent:

```python
response = client.get(
    'https://example.com/katello/api/v2/environments',
    auth=get_server_credentials(),
    verify=False,
    params={'organization_id': 5},
)
response = client.get(
    'https://example.com/katello/api/v2/organizations/5/environments',
    auth=get_server_credentials(),
    verify=False,
)
```

The above demonstrates that the API lacks orthogonality, which is bad. However,
things then get ugly. Consider this code:

```python
response = client.get(
    'https://example.com/katello/api/v2/organizations/5/environments',
    auth=get_server_credentials(),
    verify=False,
    params={'organization_id': 6},
)
```

What will happen? **We have undefined behaviour.** Rather than allowing
ourselves to make this mistake, it is best if:

* We do not provide arguments via a URL, when possible.
* We do provide arguments as JSON data, when possible.