comment out call to problematic variable

Some versions of libapparmor do not include the 'class' field for the 'aa_log_record' struct. If the user has that old library installed, then this line of code would cause a compiler issue. It caused a compiler error with some openSUSE distributions

Author: jack-ullery

src/threads/log_record.cc

@@ -120,6 +120,6 @@ std::list<std::pair<std::string, std::string>> LogRecord::get_metadata() const
   attempt_emplace_pair(metadata, "File System Type", record_data->fs_type);
   attempt_emplace_pair(metadata, "Flags", record_data->flags);
   attempt_emplace_pair(metadata, "Source Name", record_data->src_name);
-  attempt_emplace_pair(metadata, "Class", record_data->class_variable);
+  // attempt_emplace_pair(metadata, "Class", record_data->class_variable);
   return metadata;
 }