code fix and test fix for: https://issues.apache.org/jira/browse/AMQ-4225

AbortSlowConsumerStrategy was broken due to a malformed ObjectName being created when the strategy was registered on-demand. 

git-svn-id: https://svn.apache.org/repos/asf/activemq/trunk@1428051 13f79535-47bb-0310-9956-ffa450edef68