Added bug to docker related  repository tests.

'file' is not valid according to the API documentation:

> type of repo (either 'yum' or 'puppet', defaults to 'yum')

We do not use the 'file' content type in the application:

```
[ichimonji10@satqe-collab:robottelo]$ git grep \'file\'
robottelo/cli/factory.py:        u'file': '/tmp/{0}'.format(gen_alphanumeric()),
robottelo/cli/factory.py:    ssh.upload_file(local_file=layout, remote_file=args['file'])
robottelo/cli/factory.py:        u'file': '/tmp/{0}'.format(gen_alphanumeric()),
robottelo/cli/factory.py:    ssh.upload_file(local_file=layout, remote_file=args['file'])
robottelo/entities.py:        choices=('puppet', 'yum', 'file'),
robottelo/ui/locators.py:        By.XPATH, "//input[@type='file']"),
tests/foreman/cli/test_activationkey.py:                'file': manifest,
tests/foreman/cli/test_subscription.py:            'file': self.manifest,
tests/foreman/cli/test_subscription.py:            'file': self.manifest,
tests/foreman/cli/test_subscription.py:            'file': self.manifest,
tests/foreman/cli/test_subscription.py:            'file': self.manifest,
tests/foreman/cli/test_subscription.py:            'file': self.manifest,
tests/foreman/smoke/test_cli_smoke.py:            u'file': manifest,
[ichimonji10@satqe-collab:robottelo]$ git grep \"file\" | wc
      0       0       0
```

Yes, I'd vote for dropping 'file'.