util: clean up attrdict and import multiattrdict into m5.util

src/python/m5/util/__init__.py

@@ -34,7 +34,7 @@ import sys
 import convert
 import jobfile
 
-from attrdict import attrdict, optiondict
+from attrdict import attrdict, multiattrdict, optiondict
 from code_formatter import code_formatter
 from multidict import multidict
 from orderdict import orderdict

src/python/m5/util/attrdict.py

@@ -58,6 +58,9 @@ class multiattrdict(attrdict):
         try:
             return super(multiattrdict, self).__getattr__(attr)
         except AttributeError:
+            if attr.startswith('_'):
+                raise
+
             d = multiattrdict()
             setattr(self, attr, d)
             return d