##### 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

connect_timeout=30):
    config = {}
    if ssl_ca is not None or ssl_key is not None or ssl_cert is not None:
        config['ssl'] = {}
    if module.params['login_unix_socket']:
        config['unix_socket'] = module.params['login_unix_socket']
    else:
        config['host'] = module.params['login_host']
        config['port'] = module.params['login_port']
    if os.path.exists(config_file):
        config['read_default_file'] = config_file
    
    
    if login_user is not None:
        config['user'] = login_user
    if login_password is not None:
        config['passwd'] = login_password
    if ssl_cert is not None:
        config['ssl']['cert'] = ssl_cert