tc/mqprio: json-ify output

tc/mqprio: json-ify output

As reported by a Debian user, mqprio output in json mode is
invalid:

{
     "kind": "mqprio",
     "handle": "8021:",
     "dev": "enp1s0f0",
     "root": true,
     "options": { tc 2 map 0 0 0 1 0 1 0 0 0 0 0 0 0 0 0 0
          queues:(0:3) (4:7)
          mode:channel
          shaper:dcb}
}

json-ify it, while trying to maintain the same formatting
for standard output.

New output:

{
    "kind": "mqprio",
    "handle": "8001:",
    "root": true,
    "options": {
        "tc": 2,
        "map": [ 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 ],
        "queues": [ [ 0, 3 ], [ 4, 7 ] ],
        "mode": "channel",
        "shaper": "dcb"
    }
}

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=972784

Reported-by: Roméo GINON <romeo.ginon@ilexia.com>
Signed-off-by: Luca Boccassi <bluca@debian.org>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>