Don't load CLI-provided filenames immediately in Pronterface

We were still parsing the files twice for this case as the command line parser
was loading them, and the PronterWindow constructor was reloading them before
updating the UI controls.

pronsole.py

@@ -1431,7 +1431,10 @@ class pronsole(cmd.Cmd):
         self.processing_args = False
         if args.filename:
             filename = args.filename.decode(locale.getpreferredencoding())
-            self.do_load(filename)
+            self.cmdline_filename_callback(filename)
+
+    def cmdline_filename_callback(self, filename):
+        self.do_load(filename)
 
     def parse_cmdline(self, args):
         parser = argparse.ArgumentParser(description = 'Printrun 3D printer interface')

pronterface.py

@@ -1486,6 +1486,11 @@ class PronterWindow(MainWindow, pronsole.pronsole):
         threading.Thread(target = self.skein_func).start()
         threading.Thread(target = self.skein_monitor).start()
 
+    def cmdline_filename_callback(self, filename):
+        # Do nothing when processing a filename from command line, as we'll
+        # handle it when everything has been prepared
+        self.filename = filename
+
     def do_load(self,l):
         if hasattr(self, 'skeining'):
             self.loadfile(None, l)