[multipathd] 'show maps xxx' CLI tweaks

[multipathd] 'show maps xxx' CLI tweaks

o rename PRINT_MAP_FAILBACK to PRINT_MAP_STATUS
o 'print maps' command renamed to 'print maps status'
o 'print maps' now use the PRINT_MAP_NAMES layout, ie name|dm_name|wwid
o remove the dm_name field from PRINT_MAP_STATUS and PRINT_MAP_STATS