MailIT.verifyMail is failing

Before https://github.com/xwiki/xwiki-commons/commit/b61436747ed7ab311e5ff65d3f79e34e008ef93f, some functional tests (including `xwiki-platform-mail-test-docker`) were failing with a Java heap space error.
Now that the fix is applied, MailIT#verifyMail is failing on docker-all` and docker-latest, because the TestDatabaseMailListener is not loaded in the XWiki instance, and DatabaseMailListener is used instead in the test, leading to an unexpected value being found in the mail status table by selenium.