[c-nsp] BGP confusion in 12.2(18)SXE2

[Mark Boolootian]

We've been running 12.2(18)SXE2 on some sup720s for a while without issue.
Everything looks fine, but...

> I *think* this started happening when I changed the "full eBGP feed"
> session connected to this router to "no neighbour 217.71.xx.yy soft in"

I just went ahead and turned down soft-reconfiguration and, sure enough,
things got weird:

isp-g#sh ip bgp 128.132.0.0
BGP routing table entry for 128.132.0.0/16, version 11117546
Paths: (3 available, best #1, table Default-IP-Routing-Table)
  Advertised to update-groups:
     2         
  2152 3356 701 668
    137.164.24.149 from 137.164.24.149 (198.32.249.242)
      Origin IGP, metric 30, localpref 100, valid, external, best