commit: Fix use of error handling policy

Commit implemented the 'enospc' policy as 'ignore' if the error was not
ENOSPC. The QAPI documentation promises that it's treated as 'stop'.
Using the common block job error handling function fixes this and also
adds the missing QMP event.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NMax Reitz <mreitz@redhat.com>

block/commit.c

@@ -171,9 +171,9 @@ wait:
             bytes_written += n * BDRV_SECTOR_SIZE;
         }
         if (ret < 0) {
-            if (s->on_error == BLOCKDEV_ON_ERROR_STOP ||
-                s->on_error == BLOCKDEV_ON_ERROR_REPORT||
-                (s->on_error == BLOCKDEV_ON_ERROR_ENOSPC && ret == -ENOSPC)) {
+            BlockErrorAction action =
+                block_job_error_action(&s->common, false, s->on_error, -ret);
+            if (action == BLOCK_ERROR_ACTION_REPORT) {
                 goto out;
             } else {
                 n = 0;