job: Move .complete callback to Job

This moves the .complete callback that tells a READY job to complete
from BlockJobDriver to JobDriver. The wrapper function job_complete()
doesn't require anything block job specific any more and can be moved
to Job.

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

blockdev.c

@@ -3894,7 +3894,7 @@ void qmp_block_job_complete(const char *device, Error **errp)
     }
 
     trace_qmp_block_job_complete(job);
-    block_job_complete(job, errp);
+    job_complete(&job->job, errp);
     aio_context_release(aio_context);
 }