fixing cli tests

cli.test_contenthost.TestContentHost.test_positive_create_7
cli.test_product.TestProduct.test_remove_syncplan_1
cli.test_computeresource.TestComputeResource.test_update_negative
Merge pull request #1235 from alda519/cli_tests_fixes

fixed some failing cli tests
Add a test subscribing a system to a content view

Add a new test module: `tests.foreman.api.test_contentview_v2`. Add a test to
this module which does the following:

1. Create an organization, lifecycle environment and content view.
2. Publish the newly created content view.
3. Promote the newly published content view.
4. Create a system which references the organization, lifecycle environment and
   content view.

Make `ContentView.publish` raise an exception if an HTTP 4XX or 5XX response is
received. Otherwise, return a response with the JSON already decoded. Update
`tests/foreman/smoke/test_api_smoke.py` to deal with the change.