BLUEGENE - Added cnode_err_bitmap and cnode_usable_bitmap to each midplane

in the system.  cnode_err_bitmap is used to tell if there are cnodes in
an error state in the usable portion of the midplane.  cnode_usable_bitmap
is used to tell what part of the midplane is usable, typically used for
small blocks which only use a portion of a midplane.