[JIRA] (OVIRT-744) add CAPTCHA to mailman

add CAPTCHA to mailman ----------------------- Key: OVIRT-744 URL: https://ovirt-jira.atlassian.net/browse/OVIRT-744 Project: oVirt - virtualization made easy Issue Type: Improvement Reporter: Evgheni Dereveanchin Assignee: Marc Dequènes (Duck) list moderators often get joing requests from accounts that look like spambots. This ticket is to implement a CAPTCHA mechanism to check that the join request actually comes from a human.