Removed Capsule creation from smoke tests.

Our automation showed that having a `fake` Capsule created (as it was
being done by the CLI smoke tests) was causing a side effect with the
creation of `Repositories` and raising the following error:

::

  ``Action not allowed for the default capsule.``

This pull request removes the capsule creation and usage from existing
CLI smoke tests as well as updates docstrings mentioning the need for
its creation and use everywhere.

This pull request has been tested and it passed with flying colors on `qetello04`.
Merge pull request #1238 from omaciel/remove-capsule-smoke-test

Removed Capsule creation from smoke tests.
fixed failed tests
Merge pull request #1243 from sghai/fix-tests

fixed failed UI tests
Create and test robottelo.orm.EntityDeleteMixin

Create a mixin class which provides inheriting classes with a `delete` method.
Under normal circumstances, this method returns either `None` or a foreman task
ID. Add tests for this class.
Make entities and tests use orm.EntityDeleteMixin

Insert `orm.EntityDeleteMixin` into the class hierarchy of several entity
classes. (e.g. Organization and Architecture) Update the following modules to
use the new `delete` method:

* `tests/foreman/api/test_multiple_paths.py`
* `tests/foreman/api/test_role_v2.py`
* `tests/foreman/api/test_system_v2.py`