add back job.Errorf

c79b9bab54 (Remove engine.Status and replace it with standard go error)
cause a regression that create container won't get any warnings, we still
need this to send useful informations to user.

Signed-off-by: Qiang Huang <h.huangqiang@huawei.com>

engine/job.go

@@ -204,6 +204,10 @@ func (job *Job) Printf(format string, args ...interface{}) (n int, err error) {
 	return fmt.Fprintf(job.Stdout, format, args...)
 }
 
+func (job *Job) Errorf(format string, args ...interface{}) (n int, err error) {
+	return fmt.Fprintf(job.Stderr, format, args...)
+}
+
 func (job *Job) SetCloseIO(val bool) {
 	job.closeIO = val
 }