Simplify the caching of service keys to hopefully avoid the not found issue

Makes accesses simpler and reduces the number of dictionaries to one, in an effort to remove race conditions

util/expiresdict.py

@@ -38,18 +38,20 @@ class ExpiresDict(object):
       return found.value
 
     # Otherwise the key has expired or was not found. Rebuild the cache and check it again.
-    self._rebuild()
-    found = self._items.get(key)
-    if found is None:
+    items = self._rebuild()
+    found_item = items.get(key)
+    if found_item is None:
       return default_value
 
-    return found.value
+    return found_item.value
 
   def __contains__(self, key):
     return self.get(key) is not None
 
   def _rebuild(self):
-    self._items = self._rebuilder()
+    items = self._rebuilder()
+    self._items = items
+    return items
 
   def set(self, key, value, expires=None):
     self._items[key] = ExpiresEntry(value, expires=expires)