##### 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

if ssl_key is not None:
        config['ssl']['key'] = ssl_key
    if ssl_ca is not None:
        config['ssl']['ca'] = ssl_ca
    if db is not None:
        config['db'] = db
    if connect_timeout is not None:
        config['connect_timeout'] = connect_timeout
    try:
        db_connection = mysql_driver.connect(**config)
    except Exception as e:
        module.fail_json(msg="unable to connect to database: %s" % to_native(e))
    if cursor_class == 'DictCursor':
        return db_connection.cursor(**{_mysql_cursor_param: mysql_driver.cursors.DictCursor})
    else:
        return db_connection.cursor()
def mysql_common_argument_spec():
    return dict(
        login_user=dict(type='str', default=None),
        login_password=dict(type='str', no_log=True),
        login_host=dict(type='str', default='localhost'),
        login_port=dict(type='int', default=3306),
        login_unix_socket=dict(type='str'),
        config_file=dict(type='path', default='~/.my.cnf'),
        connect_timeout=dict(type='int', default=30),
        client_cert=dict(type='path', aliases=['ssl_cert']),
        client_key=dict(type='path', aliases=['ssl_key']),
        ca_cert=dict(type='path', aliases=['ssl_ca']),
    )