iproute2 bug in json output for encap

[Lars Ekman <uablrek@gmail.com>]

The destination is lost in json printout and replaced by the encap 
destination. The destination can even be ipv6 for an ipv4 route.

Example:

vm-002 ~ # ip route add 10.0.0.0/24 proto 5 dev ip6tnl6 encap ip6 dst 
fd00::192.168.2.221
vm-002 ~ # ip route show proto 5
10.0.0.0/24  encap ip6 id 0 src :: dst fd00::c0a8:2dd hoplimit 0 tc 0 
dev ip6tnl6 scope link
vm-002 ~ # ip -j route show proto 5 | jq
[
   {
     "dst": "fd00::c0a8:2dd",
     "encap": "ip6",
     "id": 0,
     "src": "::",
     "hoplimit": 0,
     "tc": 0,
     "dev": "ip6tnl6",
     "scope": "link",
     "flags": []
   }
]