bgpd: AS paths are uint32_t instead of integers

bgpd: AS paths are uint32_t instead of integers

We have some JSON output that was displaying high order
AS path data as negative numbers:

{
 "paths":[
    {
      "aspath":{
        "string":"4200010118 4200010000 20473 1299",
        "segments":[
          {
            "type":"as-sequence",
            "list":[
              -94957178,
              -94957296,
              20473,
              1299
            ]
          }
        ],

Notice "String" output -vs- the list.

With fixed code:

  "paths":[
    {
      "aspath":{
        "string":"64539 4294967000 15096 6939 7922 7332 4249",
        "segments":[
          {
            "type":"as-sequence",
            "list":[
              64539,
              4294967000,
              15096,
              6939,
              7922,
              7332,
              4249
            ]
          }
        ],

Signed-off-by: Donald Sharp <sharpd@cumulusnetworks.com>