cache_for_request should take function itself into account too

Previously it only looked at the arguments to the function, but not the
function itself.

pillar/web/utils/caching.py

@@ -1,3 +1,4 @@
+import collections
 import functools
 from flask import g
 
@@ -13,13 +14,13 @@ def cache_for_request():
         @functools.wraps(func)
         def wrapper(*args, **kwargs):
             if not hasattr(g, 'request_level_cache'):
-                g.request_level_cache = {}
+                g.request_level_cache = collections.defaultdict(dict)
 
             try:
-                return g.request_level_cache[args]
+                return g.request_level_cache[func][args]
             except KeyError:
                 val = func(*args, **kwargs)
-                g.request_level_cache[args] = val
+                g.request_level_cache[func][args] = val
                 return val
         return wrapper
     return decorator