Fixes #11089 - Adapt tests to Rails 4

This commit contains all changes to tests in branch
https://github.com/theforeman/foreman/pull/2055 that I found to be
retrocompatible with Rails 3. The more of these we can get in, the less
code we will have to review for Rails 4, and the more relevant it will...

Fixes #11035 - template preview feature

fixes #11095 - lookup keys do not get saved to db on setter invokation

Fixes #10915 - Deleting a host removes all host specific overrides

Fixes #8343 - Consolidated code paths, and removed unnecessary DB calls for parent object

Fixes #11078 - Substitute find_all_by by where to comply with Rails 4

This commit takes away all instances up to this point of find_all_by to
improve Rails 4 compatibility. They are substituted by .where calls.

Fixes #10356 - changed the POST/PUT RABL template to be the same as the GET template

HTTP response code standardized to 201 on create.

Fixes #10438 - Removed trends:clean task, as it is no longer needed

Fixes #11025: Allow skip test runner to run through Jenkins test task.

The Jenkins CI gem implements its own custom test runner. When trying
to use a custom test runner in the jenkins environment, this test
runner needs to be inherited from and included as the last argument....

Fixes #10867 - OpenStack boot_from_volume is true only when checked