Validation errors when MariaDB is used

Versions

• Ubuntu 16.04
• MariaDB 10.0.27
• Virtualmin 5.05 (occurred in 5.04 as well)

Steps to reproduce:

1. Create a virtual server with "MySQL" database enabled (this creates a MariaDB table)
2. Run virtual server validation
3. The error is "MySQL database : MySQL login example does not exist".

Description

This is a relatively recent issue, only coming up in the past few months or so. Servers created several months ago pass validation without issue. Servers created today fail validation.

When inspecting the "user" table of the "mysql" database, the password field is blank. VM seems to place the password in "authentication_string" and also fills the "plugin" field. I can clear the validation error by copying the password in the "authentication_string" into the "Password" field and blanking both the "authentication_string" and "plugin" fields.