HORNETQ-1446 / BZ-1158920 - Internal error during UDP parsing

https://bugzilla.redhat.com/show_bug.cgi?id=1158920
https://issues.jboss.org/browse/HORNETQ-1446

The DiscoveryGroup should be resilient to failures on the communication.
We shouldn't kill the Loop if an exception happened during the read of the UDP messages.