##### 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

"""Class for collection MySQL instance information.
    Arguments:
        module (AnsibleModule): Object of AnsibleModule class.
        cursor (pymysql/mysql-python): Cursor class for interaction with
            the database.
    Note:
        If you need to add a new subset:
        1. add a new key with the same name to self.info attr in self.__init__()
        2. add a new private method to get the information
        3. add invocation of the new method to self.__collect()
        4. add info about the new subset to the DOCUMENTATION block
        5. add info about the new subset with an example to RETURN block
    """
    def __init__(self, module, cursor):
        self.module = module
        self.cursor = cursor
        self.info = {
            'version': {},
            'databases': {},
            'settings': {},
            'global_status': {},
            'engines': {},
            'users': {},
            'master_status': {},
            'slave_hosts': {},
            'slave_status': {},
        }
    def get_info(self, filter_, exclude_fields):