NO-JIRA: HA documentation: security configuration troubleshooting

Common issue for new users is cluster failing to start due to incorrect
security configuration. Added some notes to highlight the need for
security configuration and updated the troubleshooting section.

git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk@1598315 13f79535-47bb-0310-9956-ffa450edef68