qapi event: convert other BLOCK_JOB events

Since BLOCK_JOB_COMPLETED, BLOCK_JOB_CANCELLED, BLOCK_JOB_READY are
related, convert them in one patch. The block_job_event_* functions
are used to keep encapsulation of BlockJob structure.

Signed-off-by: Wenchao Xia <wenchaoqemu@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
diff --git a/blockdev.c b/blockdev.c
index 9b0f8ac..03ab153 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -1847,23 +1847,21 @@
 static void block_job_cb(void *opaque, int ret)
 {
     BlockDriverState *bs = opaque;
-    QObject *obj;
+    const char *msg = NULL;
 
     trace_block_job_cb(bs, bs->job, ret);
 
     assert(bs->job);
-    obj = qobject_from_block_job(bs->job);
+
     if (ret < 0) {
-        QDict *dict = qobject_to_qdict(obj);
-        qdict_put(dict, "error", qstring_from_str(strerror(-ret)));
+        msg = strerror(-ret);
     }
 
     if (block_job_is_cancelled(bs->job)) {
-        monitor_protocol_event(QEVENT_BLOCK_JOB_CANCELLED, obj);
+        block_job_event_cancelled(bs->job);
     } else {
-        monitor_protocol_event(QEVENT_BLOCK_JOB_COMPLETED, obj);
+        block_job_event_completed(bs->job, msg);
     }
-    qobject_decref(obj);
 
     bdrv_put_ref_bh_schedule(bs);
 }