Don't template play vars by themselves, it's too early

##### Summary

Templating the play variables before the rest of the variables are loaded can lead to wrong results in variables.

##### Example inventory:

```
localhost ansible_connection=local
[all:vars]
var=value
```

##### Example playbook:

```
---
- name: Default value for inventory variable
  hosts: localhost
  gather_facts: no
  vars:
    var2: "{{ var  | default('none') }}"
  tasks:
    - debug: var=var
    - debug: var=var2
```

##### Expected results:

```
PLAY [Default value for inventory variable] *********************************** 

TASK: [debug var=var] ********************************************************* 
ok: [localhost] => {
    "var": "value"
}

TASK: [debug var=var2] ******************************************************** 
ok: [localhost] => {
    "var2": "value"
}
```

##### Actual results:

```
PLAY [Default value for inventory variable] *********************************** 

TASK: [debug var=var] ********************************************************* 
ok: [localhost] => {
    "var": "value"
}

TASK: [debug var=var2] ******************************************************** 
ok: [localhost] => {
    "var2": "none"
}
```