cmd: shorten the locking window when using --progress to avoid deadlock

Before this change, using -P occasionally deadlocked on the progress
mutex and the stats mutex since they call each other.

This is fixed by shortening the locking window in the progress routine
so as not to include the stats calculation.

cmd/progress.go

@@ -84,9 +84,6 @@ var (
 
 // printProgress prints the progress with an optional log
 func printProgress(logMessage string) {
-	progressMu.Lock()
-	defer progressMu.Unlock()
-
 	var buf bytes.Buffer
 	w, h, err := terminal.GetSize(int(os.Stdout.Fd()))
 	if err != nil {
@@ -100,6 +97,10 @@ func printProgress(logMessage string) {
 		buf.WriteString(s)
 	}
 
+	// Lock from here to prevent terminal corruption
+	progressMu.Lock()
+	progressMu.Unlock()
+
 	if logMessage != "" {
 		out("\n")
 		out(moveUp)