Issue Summary

When doing a Jira vanilla install using mysql, if we do use an user already used by another database, Jira setup fails with the error:

Steps to Reproduce

• new install of Jira 8.16/8.13.6,mysql-connector-java-8.0.22.jar
  jira-home folder created
• create a new database: CREATE DATABASE jiradb816 CHARACTER SET utf8mb4 COLLATE utf8mb4_bin;
• get a database user created earlier and used by another Jira Database and just grant access to this new DB: GRANT SELECT,INSERT,UPDATE,DELETE,CREATE,DROP,REFERENCES,ALTER,INDEX on jiradb816.* TO 'jiradbuser'@'localhost';
• start Jira. It will land at the setup mode
• Select your own install and database
• Fill with the new Database created jiradb816 and the user jiradbuser and hit the test connection button

Expected Results

• test successful, we are able to proceed with the install

Actual Results

• Test fails with the error message and we can not hit next.

  You have specified a database that is not empty, please specify an empty database. If you want to upgrade an existing installation, please follow these instructions instead.

Workaround

• Delete all content of Jira home folder
• Drop DB, create new user, create new DB, and grant access:

  drop database jiradb816;
  create user 'jira-816'@'localhost' IDENTIFIED BY 'jira-816';
  CREATE DATABASE jiradb816 CHARACTER SET utf8mb4 COLLATE utf8mb4_bin;
  GRANT SELECT,INSERT,UPDATE,DELETE,CREATE,DROP,REFERENCES,ALTER,INDEX on jiradb816.* TO 'jira-816'@'localhost';
  flush privileges;