Adjust various struct field names and their respective calls.

Per golint:

  canaryd.go:26:2: struct field Id should be ID
  canaryd.go:27:2: struct field Url should be URL
  canaryd.go:32:2: struct field Id should be ID
  canaryd.go:36:2: struct field HttpStatus should be HTTPStatus
  canaryd.go:37:2: struct field LocalIp should be LocalIP
  canaryd.go:38:2: struct field PrimaryIp should be PrimaryIP