count no worthwhile cached data as a miss, even if the varibale has
been initialized
only save cache results when we actually got data back, otherwise we
will cache an empty array and not try again
request the full index even if something has already included get_ganglia

Otherwise we will only have the data from the 'view' (for example)
context for a view as opposed to the full index it likely requires
Merge pull request #189 from cburroughs/json-cache-robustness

cache robustness