Stop ignoring missing object variables

[otakup0pe]

When passing in a complex structure, it seems that aomi doesn't mind if it's sub variables are missing. We want to enforce the use of the Jinja2 default filter for default variables - not fall back to an empty string.

For example,

# var file
foo:
- val1: test1
  val2: test2
- val1: test3

#Secretfile
mounts:
{% for v in foo %}
- path: "{{v.val1}}/{{v.val2}}"
{% endfor -%}

This example will result in two mountpoints being created - test1/test2 and test3 when in reality we would want this specific example to fail based on val2 not being set.