Add the ability to abort the running test job

[ryojiosawa]

Cinnamon currently does not provide the ability to abort the test job that's already scheduled or running. This means, once you submit a test run, there's no other option but to wait until the job is done, which may not be ideal especially when you're running a suite of many tests. Cinnamon should at least provide the ability to cancel or abort the test job that's already running.