This greatly refactors the tests to unify a lot. It uses a lot of
parameter inheritance to avoid duplication.

Fix wrong variable name in enc function

This further unifies the tests and removes redundant workarounds.

This decouples the tests from a Puppet CA which may not always be
present.

Since Foreman 97c34475c9e674db6443b28e03a5e4d94d585f2e (1.10+) this is
actually a boolean. The string 'off' would be interpreted as the value
true.

Because we're trying to move people away from the latest repository, we
set it to configure an explicit version with a default. Because this
default would need to be updated all the time, it's a bad idea.

This patch removes the $custom_repo and makes $repo undef by default.
This means users get no repository by default and need to explicitly
choose which repository to use.