Revert nested hash indifference, swap delete order

Upstream doesnt support nested hashes having indifferent access, we
should stay consistent. Swap order for returned value in session hash.

actionpack/lib/action_controller/flash.rb

@@ -95,12 +95,7 @@ module ActionController #:nodoc:
       end
 
       def [](k)
-        v = super(k.to_s)
-        if v.is_a? Hash
-          v.with_indifferent_access
-        else
-          v
-        end
+        super(k.to_s)
       end
 
       def delete(k)

actionpack/lib/action_controller/session/abstract_store.rb

@@ -89,7 +89,7 @@ module ActionController
           load_for_write!
           value = super(key)
           string_value = super(key.to_s)
-          value || string_value
+          string_value || value
         end
 
         def data