backup: Fix shutdown hang when running in the background

On shutdown the backup commands waits for the terminal output goroutine
to stop. However while running in the background the goroutine ignored
the canceled context.

internal/ui/termstatus/status.go

@@ -96,11 +96,9 @@ func (t *Terminal) run(ctx context.Context) {
 	for {
 		select {
 		case <-ctx.Done():
-			if IsProcessBackground(t.fd) {
-				// ignore all messages, do nothing, we are in the background process group
-				continue
+			if !IsProcessBackground(t.fd) {
+				t.undoStatus(len(status))
 			}
-			t.undoStatus(len(status))
 
 			return