##### 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

"""Get slave status if the instance is a slave."""
        res = self.__exec_sql('SHOW SLAVE STATUS')
        if res:
            for line in res:
                host = line['Master_Host']
                if host not in self.info['slave_status']:
                    self.info['slave_status'][host] = {}
                port = line['Master_Port']
                if port not in self.info['slave_status'][host]:
                    self.info['slave_status'][host][port] = {}
                user = line['Master_User']
                if user not in self.info['slave_status'][host][port]:
                    self.info['slave_status'][host][port][user] = {}
                for vname, val in iteritems(line):
                    if vname not in ('Master_Host', 'Master_Port', 'Master_User'):
                        self.info['slave_status'][host][port][user][vname] = self.__convert(val)
    def __get_slaves(self):
        """Get slave hosts info if the instance is a master."""
        res = self.__exec_sql('SHOW SLAVE HOSTS')
        if res:
            for line in res:
                srv_id = line['Server_id']
                if srv_id not in self.info['slave_hosts']:
                    self.info['slave_hosts'][srv_id] = {}
                for vname, val in iteritems(line):
                    if vname != 'Server_id':
                        self.info['slave_hosts'][srv_id][vname] = self.__convert(val)
    def __get_users(self):