Possible thread contention on Collectd due to the checking on datacollection-config changes.

The attached thread dump shows that when Collectd is using a large amount of threads (700 in this example), there are situations on which Collectd might freeze itself when all the threads are trying to access some data from the SNMP data collection configuration; because when this happen, the configuration DAO is going to verify if the datacollection-config.xml has been changed or node on every single call.

This is related with the following customer support ticket:
http://mynms.opennms.com/Ticket/Display.html?id=2525