bgpd: readjust fields in evpn vni json cmd

bgpd: readjust fields in evpn vni json cmd

1) Keep consistant field name, such as
"inKernel".
2) Keep fields order same for both outputs.

Testing Done:

TORS1# show bgp l2vpn evpn vni json
{
  "advertiseGatewayMacip":"Disabled",
  "advertiseSviMacip":"Disabled",
  "advertiseAllVnis":"Enabled",
  "flooding":"Head-end replication",
  "numVnis":8,
  "numL2Vnis":5,
  "numL3Vnis":3,
  "1002":{
    "vni":1002,
    "type":"L2",
    "inKernel":"True",
    "rd":"27.0.0.15:8",
    "originatorIp":"27.0.0.15",
    "mcastGroup":"0.0.0.0",
    "advertiseGatewayMacip":"Disabled",
    "advertiseSviMacip":"Disabled",
    "importRTs":[
      "5550:1002"
    ],
    "exportRTs":[
      "5550:1002"
    ]
  },
}

TORS1# show bgp l2vpn evpn vni 1002 json
{
  "vni":1002,
  "type":"L2",
  "inKernel":"True",
  "rd":"27.0.0.15:8",
  "originatorIp":"27.0.0.15",
  "mcastGroup":"0.0.0.0",
  "advertiseGatewayMacip":"Disabled",
  "advertiseSviMacip":"Disabled",
  "importRts":[
    "5550:1002"
  ],
  "exportRts":[
    "5550:1002"
  ]
}

Signed-off-by: Chirag Shah <chirag@cumulusnetworks.com>