##### 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 user info."""
        res = self.__exec_sql('SELECT * FROM mysql.user')
        if res:
            for line in res:
                host = line['Host']
                if host not in self.info['users']:
                    self.info['users'][host] = {}
                user = line['User']
                self.info['users'][host][user] = {}
                for vname, val in iteritems(line):
                    if vname not in ('Host', 'User'):
                        self.info['users'][host][user][vname] = self.__convert(val)
    def __get_databases(self, exclude_fields):
        """Get info about databases."""
        if not exclude_fields:
            query = ('SELECT table_schema AS "name", '
                     'SUM(data_length + index_length) AS "size" '
                     'FROM information_schema.TABLES GROUP BY table_schema')
        else:
            if 'db_size' in exclude_fields:
                query = ('SELECT table_schema AS "name" '
                         'FROM information_schema.TABLES GROUP BY table_schema')
        res = self.__exec_sql(query)
        if res:
            for db in res:
                self.info['databases'][db['name']] = {}
                if not exclude_fields or 'db_size' not in exclude_fields:
                    self.info['databases'][db['name']]['size'] = int(db['size'])
    def __exec_sql(self, query, ddl=False):