Fix an invalid reference when loading initial state for the cache type.
Review Request #8454 — Created Oct. 11, 2016 and submitted
If the site configuration didn't contain information for the memory cache server type, the form code would try to load the initial value from the form. This failed due to accessing this from the wrong location, resulting in a HTTP 500. This change fixes that to load from the correct location.
Loaded the page successfully. (Not sure where my cache info went.)
Tool: Pyflakes Processed Files: reviewboard/admin/forms.py Tool: PEP8 Style Checker Processed Files: reviewboard/admin/forms.py