1094470 - Canceling a task that was already in a completed state now results in a 200 code instead of a 500

https://bugzilla.redhat.com/show_bug.cgi?id=1094470
The constants.CALL_COMPLETE_STATES that causes this branch to be taken could be because of more cases than the task being completed. I looked in constants and it could be in an errors state, skipped, already cancelled (this case), finished timed_out, etc.

Perhaps adjust the the log to say the task already reached a final state and include what that state is. Otherwise the logs could show a task that was cancelled or errored, etc as completed.