mirror: Quit after showing all progressbar updates (#2020)

mc can quit when mirror terminates but progress bar is not able
to show all made progress. This commit makes mc waits until all updates
are sent to the status channel.

cmd/mirror-main.go

@@ -272,6 +272,12 @@ func (mj *mirrorJob) startStatus() {
 	}()
 }
 
+// Stop status go routine, further updates could lead to a crash
+func (mj *mirrorJob) stopStatus() {
+	close(mj.statusCh)
+	mj.wgStatus.Wait()
+}
+
 // this goroutine will watch for notifications, and add modified objects to the queue
 func (mj *mirrorJob) watchMirror() {
 
@@ -484,6 +490,9 @@ func (mj *mirrorJob) mirror() {
 	if mj.isWatch {
 		<-mj.trapCh
 	}
+
+	// Wait until all progress bar updates are actually shown and quit.
+	mj.stopStatus()
 }
 
 func newMirrorJob(srcURL, dstURL string, isFake, isRemove, isWatch, isForce bool) *mirrorJob {