Log nice error messages when creating a socket fails

Just spent quite a while trying to debug why a certain server test case didn't start. It was because I was exceeding the number of allowed FD's however powerdns was just dumping. If it had logged these error messages it would have been a lot quicker to debug! For some reason the PDNSException is not being properly handled when it occurs (terminate called recursively) so the below is a nice simple workaround to ensure that something at least hits the logs.

Mark