BGP: Display the right reason code for session reset

BGP: Display the right reason code for session reset

Ticket: CM-7439
Reviewed By: Donald Sharp
Testing Done:

If a session was reset due to a NOTIFICATION the "show ip bgp
neighbor" output would not display details on what the
notification actually was.  This patch changes that.  Example:

superm-redxp-05# show ip bgp neighbors 20.1.2.2
BGP neighbor is 20.1.2.2, remote AS 21, local AS 10, external link
[snip]
  Last reset 01:05:07, due to NOTIFICATION sent (OPEN Message Error/Bad Peer AS)