##### 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

"""Execute SQL.
        Arguments:
            ddl (bool): If True, return True or False.
                Used for queries that don't return any rows
                (mainly for DDL queries) (default False).
        """
        try:
            self.cursor.execute(query)
            if not ddl:
                res = self.cursor.fetchall()
                return res
            return True
        except Exception as e:
            self.module.fail_json(msg="Cannot execute SQL '%s': %s" % (query, to_native(e)))
        return False
#
def main():
    argument_spec = mysql_common_argument_spec()
    argument_spec.update(
        login_db=dict(type='str'),
        filter=dict(type='list'),
        exclude_fields=dict(type='list'),
    )