Add repository CLI tests for checksum type option

Add create and update tests that ensures that checksum type is defined
as expected.

Skip tests due to BZ as the checksum type is not shown in the hammer
repository info output.

Bonus: some formatting improvements

Closes #1573
Fix or skip tests for /config_templates API path

The `/config_templates` API path incorrectly rejects some parameters. Skip some
tests that fail due to this issue. For more information, see:

* https://bugzilla.redhat.com/show_bug.cgi?id=1154156
* http://projects.theforeman.org/issues/7989

The API documentation also states that all POST requests to the
`/config_templates` path should be wrapped in an extra hash. Do so.

These two changes fix a number of failing tests. Updated test results:

    $ nosetests tests/foreman/api/test_multiple_paths.py -m ConfigTemplate
    InsecureRequestWarning)
    .SS..S..SS
    ----------------------------------------------------------------------
    Ran 10 tests in 7.735s

    OK (SKIP=5)
Merge pull request #1606 from Ichimonji10/config-templates

Fix or skip tests for /config_templates API path
Merge pull request #1605 from elyezer/checksum-type-tests

Add repository CLI tests for checksum type option
Use ``busybox`` for Docker-based tests.

Instead of using the ``wordpress`` Docker image for our existing tests,
I am proposing that we switch to using the ``busybox`` image since it is
much smaller and should speed up our tests.

I have not run our tests but I did manually try it using latest build
with success.
Merge pull request #1608 from omaciel/master

Use ``busybox`` for Docker-based tests.