Fix LifecycleEnvironment.{build,create}

> When a new lifecycle environment is created, it must either:
>
> * Reference some other lifecycle environment via the "prior" field.
> * Have a name of "Library". Note that within a given organization, there
>   can only be a single lifecycle environment with a name of "Library".

Override method `LifecycleEnvironment.build`, thus allowing one to easily create
new lifecycle environments. Incidentally, this also prevents a recursive death
spiral from occurring when `build` or `create` are called.

Update `tests/foreman/api/test_multiple_paths.py` to take advantage of this
change.
Just a quick thought. I could writhe something like this?

```python
query_results = client.get(
    self.path(),
    auth=get_server_credentials(),
    verify=False,
    params={
        'name': 'Library',
        'organization_id': self.organization,
    }
).json()['results']
if len(query_results) == 0:
    raise FactoryError('No default LifecycleEnvironment exists for Organization {0}.'.format(self.organization))
self.prior = query_results[0]['id']
```