Code review comment for ~ltrager/maas:health_status

As discussed this branch no longer calculates the overall health status by looking at the testing and commissioning results. Instead the health status is the testing status.

To produce the testing_status, cpu_status, memory_status and storage_status in the API I need to cache and iterate through all ScriptResults on the node. As I'm doing that I capture the overall commissioning status and output everything in the API. This gives the API and UI feature parity with regards to status.

In the websocket I noticed we were not calculating the testing_status or commissioning_status from cache. I modified the code to calculate both from cache the values are still the same.