Broken Links Checker: don't log into audit-log

Issue originally reported by Bart as HIPCON-916:

The hippo-audit log is flooded with messages from the broken links checker:
16.09.2013 00:00:09 INFO [org.hippoecm.repository.audit.AuditLogger.logHippoEvent():39] {"application":"repository","interactionId":"e1334be2-303e-45ef-a6ef-16ce482fd519","documentPath":"/content/documents/onehippo-deutsch/ueber-uns/nachrichten/2011/06/hippo-is-expanding-in-germany-with-new-partner-satzmedia/hippo-is-expanding-in-germany-with-new-partner-satzmedia","interaction":"brokenlinks:checkbrokenlinks:checkLinks","timestamp":1379282409544,"category":"workflow","arguments":["[Link

{url='http://www.satzmedia.de/', isBroken=true, resultCode=1000, resultMessage='java.net.SocketTimeoutException', resultException=null, broken=true}

]"],"workflowName":"reportbrokenlinks","action":"org.onehippo.cms7.brokenlinks.ReportBrokenLinksWorkflowImpl.reportBrokenLinks","handleUuid":"fdee2b11-6439-4728-8561-bf53312dceb1","className":"org.onehippo.cms7.brokenlinks.ReportBrokenLinksWorkflowImpl","user":"system","methodName":"reportBrokenLinks","workflowCategory":"brokenlinks"}

I've no idea why it was decided to have these messages in the audit log. In my opinion that is wrong. The audit log is generally about creating a trace of people doing something