Auditing History purge does not work with "Retain Failures" enabled (JIRA 7.x)

Problem

The audit history purge operation fails when the "retain failures" setting is enabled. 

Solution

There is no current solution to this problem. The AO streaming API that is provided by Atlassian is "buggy", and means that our once-efficient data reading is not possible (https://ecosystem.atlassian.net/browse/AO-694).  As a result, we have made the decision to remove this purge setting in newer versions of JEMH.