OG Menu names that start with menu- don't get associated with the group

To reproduce:

1. When looking at a group node (node/GID) visit node/GID/og_menu/add
2. Enter menu-GID-another-menu for the Menu name and fill in the title and description fields
3. Submit the form
4. It looks like everything is fine, but now if you visit node/GID/og_menu you won't see your new menu listed
5. Check the datatabase tables -- in og_menu, your new menu will have menu_name of menu-GID-another-menu which is what we want. In menu_custom, the new menu will have menu_name of menu-menu-GID-another-menu (note the additional menu- prepended)

The fix is probably to strip off menu- when submitting the form, but I haven't looked closely enough at the code yet. The query in og_menu_overview_page() is joining menu_custom and og_menu on menu_name, which is why we can't see the newly added menu.