[COOK-3701] Use pure node attributes in `_apache_common` and `apache_jenkins` templates

Originally presented in
https://github.com/opscode-cookbooks/jenkins/commit/65cefad7259fe6dd75bd89643a2ebf6211b56cc3#commitcomment-4222187,
a refactor due to a foodcritic recipe removed a template variable that was
being used by a nested partial. Switching to node attributes eliminates this
problem, makes foodcritic happy, and prevents people from questioning "now
where did that variable come from?"