Fix error of cannot login to phpMyAdmin due plugin changes

In MySQL 5.7 (released Oct 2015) and MySQL 8, the root MySQL user is set to authenticate using the auth_socket or caching_sha2_password plugin rather than with mysql_native_password. This will prevent programs like phpMyAdmin from logging in with the root account.

The fix for this:

mysql> UPDATE mysql.user SET plugin = 'mysql_native_password', authentication_string = PASSWORD('changeme') WHERE User = 'root';