Fix unloading of Norm records without benchmark

Fix unlaoding of normalised summaries that don't have a
benchmark/servicelevel type set by corecing them to HEPSPEC to maintain
historical records.

apel/db/records/record.py

@@ -299,6 +299,8 @@ def get_msg(self, withhold_dns=False):
             if key in self._dict_fields:
                 # Create dictionary fields for v0.4 message formats.
                 benchmark_type = self._record_content['ServiceLevelType']
+                if benchmark_type is None:
+                    benchmark_type = "HEPSPEC"
                 msg += key+ ": {" + benchmark_type + ": " + value + "}\n"
             else:
                 # otherwise, add the line