GtkFileChooser: don't override already opened folder

When filechooer is re-used (instead of being created and destroyed
every time it's needed), it might happen that the directory the
application wishes to initially show is the same directory that
was shown last time the filechooser was used. In that case, make sure
filechooser knows that it does not need to do its default "select $pwd
or $home" routine.

https://bugzilla.gnome.org/show_bug.cgi?id=766122

gtk/gtkfilechooserwidget.c

@@ -5666,6 +5666,9 @@ gtk_file_chooser_widget_select_file (GtkFileChooser  *chooser,
       files.data = (gpointer) file;
       files.next = NULL;
 
+      /* Prevent the file chooser from loading a different folder when it is mapped */
+      priv->reload_state = RELOAD_HAS_FOLDER;
+
       result = show_and_select_files (impl, &files);
       g_object_unref (parent_file);
       return result;