Pull labs: Support state transitions

[bhcopeland]

We need a API call added to KernelCI to allow for pull labs to modify the state: field. Right now it isn't possible to modify, and we need to send a call back to the API to say state: done. Right now KCI runs with state: running, then state: complete.

Pull labs needs to support State change so we know the job has been executed/finished

[ivoire]

Will be good to have an option to filter by state when listing events in the API.