job: Move cancelled to Job

We cannot yet move the whole logic around job cancelling to Job because
it depends on quite a few other things that are still only in BlockJob,
but we can move the cancelled field at least.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>

tests/test-blockjob.c

@@ -179,7 +179,7 @@ static void coroutine_fn cancel_job_start(void *opaque)
     CancelJob *s = opaque;
 
     while (!s->should_complete) {
-        if (block_job_is_cancelled(&s->common)) {
+        if (job_is_cancelled(&s->common.job)) {
             goto defer;
         }