[multipathd] add "show map $map topo" CLI command

[multipathd] add "show map $map topo" CLI command

multipathd> sho map dm-1 topo
mpath0 (149455400000000000000000000000000d00600000b000000)
[size=67 GB][features=1 queue_if_no_path][hwhandler=0]
\_ round-robin 0 [prio=10][enabled]
 \_ 3:0:0:1 sdb 8:16 [active][ready]
\_ round-robin 0 [prio=6][enabled]
 \_ 4:0:0:1 sde 8:64 [active][ready]

and :

multipathd> sho map mpath0 topo
mpath0 (149455400000000000000000000000000d00600000b000000)
[size=67 GB][features=1 queue_if_no_path][hwhandler=0]
\_ round-robin 0 [prio=0][enabled]
 \_ 3:0:0:1 sdb 8:16 [active][ready]
\_ round-robin 0 [prio=0][enabled]
 \_ 4:0:0:1 sde 8:64 [active][ready]