##### SUMMARY
mysql_user module with check_implicit_admin=yes try to connect to database without password. But when login failed doesn't fallback to login_user and login_password credentials.

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
mysql_user

##### ANSIBLE VERSION
```
2.9.0
```

##### OS / ENVIRONMENT
Ubuntu 18.04

##### STEPS TO REPRODUCE
```yaml
- name: Update root password for all root accounts
  mysql_user: name=root password={{ mysql_root_password }} login_user=root login_password={{ mysql_root_password }} host={{ item }} check_implicit_admin=yes
  with_items:
    - "{{ current_hostname.stdout | lower }}"
    - 127.0.0.1
    - ::1
    - localhost
```

First run is ok, but on second run Ansible failed when try to connect as root without password and no fallback to login credentials.

##### EXPECTED RESULTS
First run -> root / no password
Other runs -> root / mysql_root_password

##### ACTUAL RESULTS
Provision failed at other as first run

module = AnsibleModule(
        argument_spec=argument_spec,
        supports_check_mode=True,
    )
    db = module.params['login_db']
    connect_timeout = module.params['connect_timeout']
    login_user = module.params['login_user']
    login_password = module.params['login_password']
    ssl_cert = module.params['client_cert']
    ssl_key = module.params['client_key']
    ssl_ca = module.params['ca_cert']
    config_file = module.params['config_file']
    filter_ = module.params['filter']
    exclude_fields = module.params['exclude_fields']
    if filter_:
        filter_ = [f.strip() for f in filter_]
    if exclude_fields:
        exclude_fields = set([f.strip() for f in exclude_fields])
    if mysql_driver is None:
        module.fail_json(msg=mysql_driver_fail_msg)
    cursor = mysql_connect(module, login_user, login_password,
                           config_file, ssl_cert, ssl_key, ssl_ca, db,
                           connect_timeout=connect_timeout, cursor_class='DictCursor')
    
    
    mysql = MySQL_Info(module, cursor)
    module.exit_json(changed=False, **mysql.get_info(filter_, exclude_fields))
if __name__ == '__main__':
    main()