This change is similar to https://github.com/ansible/ansible/pull/10465

It extends the logic there to also support none types.  Right now if you have
a '!!null' in yaml, and that var gets passed around, it will get converted to
a string.

eg. defaults/main.yml
```
ENABLE_AWESOME_FEATURE: !!null # Yaml Null
OTHER_CONFIG:
  secret1: "so_secret"
  secret2: "even_more_secret"

CONFIG:
  hostname: "some_hostname"
  features:
    awesame_feature: "{{ ENABLE_AWESOME_FEATURE}}"
  secrets: "{{ OTHER_CONFIG }}"
```

If you output `CONFIG` to json or yaml, the feature flag would get represented in the output
as a string instead of as a null, but secrets would get represented as a dictionary.  This is
a mis-match in behaviour where some "types" are retained and others are not.  This change
should fix the issue.

I also updated the template test to test for this and made the changes to v2.

Added a changelog entry.