Run keys through Jinja

Previously, only values were run through Jinja, which meant that, for
example, tag names in the ec2_tag module, which were specified as keys,
couldn't be dynamically generated.

This change allows a task like the following:

```
- name: Set role state tag
  local_action: ec2_tag resource={{ ec2_id }} region=us-east-1
  args:
    tags:
      role-{{ service }}: "{{ 'started' if result.rc == 1 else 'stopped' }}"
```

Previously, the "{{ service }}" would be passed through as part of the
EC2 tag name.