### Summary

If a var is defined in the `vars:` of a block, and then redefined again in the `vars:` of an inner block, the outer value is still used.

`vars:` on a _task_ in the inner block work as expected.

### Issue Type

Bug Report

### Component Name

unknown

### Ansible Version

```console
$ ansible --version
ansible [core 2.12.0.dev0] (devel 1fc1ab89ae) last updated 2021/07/17 12:29:56 (GMT -400)
  config file = None
  configured module search path = ['/home/briantist/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /home/briantist/code/ansible/ansible.core/lib/ansible
  ansible collection location = /home/briantist/.ansible/collections:/usr/share/ansible/collections
  executable location = /home/briantist/code/ansible/ansible.core/bin/ansible
  python version = 3.6.9 (default, Jan 26 2021, 15:33:00) [GCC 8.4.0]
  jinja version = 3.0.1
  libyaml = True
```


### Configuration

```console
$ ansible-config dump --only-changed
CALLBACKS_ENABLED(env: ANSIBLE_CALLBACK_WHITELIST) = ['profile_tasks']
DEFAULT_FORKS(env: ANSIBLE_FORKS) = 30
INVENTORY_ENABLED(env: ANSIBLE_INVENTORY_ENABLED) = ['host_list', 'auto', 'ini', 'yaml', 'toml']
```


### OS / Environment

Ubuntu 18.04 on WSL2

### Steps to Reproduce

<!--- Paste example playbooks or commands between quotes below -->
```yaml
- name: outer
  vars:
    myvar: abc
  block:
    - debug:
        var: myvar

    - name: inner block
      vars:
        myvar: 123
      block:

        - debug:
            var: myvar

        - name: task
          vars:
            myvar: xyz
          debug:
            var: myvar
```

### Expected Results

inner block first `debug` result is `123`

### Actual Results

inner block first `debug` result is `abc`


### Code of Conduct

- [X] I agree to follow the Ansible Code of Conduct
'''
        Generic logic to get the attribute or parent attribute for a block value.
        '''
        extend = self._valid_attrs[attr].extend
        prepend = self._valid_attrs[attr].prepend
        try:
            value = self._attributes[attr]
            
            
            if getattr(self._parent, 'statically_loaded', True):
                _parent = self._parent
            else:
                _parent = self._parent._parent
            if _parent and (value is Sentinel or extend):
                try:
                    if getattr(_parent, 'statically_loaded', True):
                        if hasattr(_parent, '_get_parent_attribute'):
                            parent_value = _parent._get_parent_attribute(attr)
                        else:
                            parent_value = _parent._attributes.get(attr, Sentinel)
                        if extend:
                            value = self._extend_value(value, parent_value, prepend)
                        else:
                            value = parent_value
                except AttributeError:
                    pass
            if self._role and (value is Sentinel or extend):
                try:
                    parent_value = self._role._attributes.get(attr, Sentinel)
                    if extend: