##### 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

mysql_info:
    login_user: mysuperuser
    login_password: mysuperpass
    filter: version
- name: Collect all info except settings and users by root
  mysql_info:
    login_user: root
    login_password: rootpass
    filter: "!settings,!users"
- name: Collect info about databases and version using ~/.my.cnf as a credential file
  become: yes
  mysql_info:
    filter:
    - databases
    - version
- name: Collect info about databases and version using ~alice/.my.cnf as a credential file
  become: yes
  mysql_info:
    config_file: /home/alice/.my.cnf
    filter:
    - databases
    - version
- name: Collect info about databases excluding their sizes
  become: yes
  mysql_info:
    config_file: /home/alice/.my.cnf
    filter:
    - databases
    exclude_fields: db_size
'''