Settle the great finish_task() and finish_task_new() debate.

Rename finish_task_new() to finish_task() and remove the old finish_task().
When both running a service locally and finishing that task and calling the
API to finish a task they will both now call finish_task().

Also, remove _add_file(). If services want to add files they can use
the exposed handlers accordingly.

This allows us to simplify things. There is no more finalize() function as
we don't need to add files now. If the service is not distributed we will
automatically finish the task for them. If the service is distributed it
will now need to call self.current_task.finish() instead of self.finalize().

Also, remove unused 'c' variable in update_analysis_results() and fix
whitespace.