Change to $HOME before launching gnome-panel again

When exiting from --replace mode, we want to start the new
gnome-panel with a reasonable working directory so that if, you say,
open a terminal from it it doesn't start off in the gnome-shell
directory.

(gnome-shell itself is running in $HOME because mutter changes
directory itself at startup.)

Reported by Mathieu Bridon
http://bugzilla.gnome.org/show_bug.cgi?id=591145

src/gnome-shell.in

@@ -301,6 +301,11 @@ finally:
 
     if not run_in_xephyr:
         # Restart gnome-panel and window manager
+
+        # We don't want to start the new gnome-panel in the current
+        # directory; $HOME is better for stuff launched from it
+        os.chdir(os.path.expanduser("~"))
+
         if metacity_pid:
             if options.verbose:
                 print "Restarting Metacity"