bgp: fix case where confederation id same as member-as

bgp:  fix case where confederation id same as member-as

currently the following configuration

dut:

!
interface ntfp2
 ip router isis 1
!
router bgp 200
 no bgp ebgp-requires-policy
 bgp confederation identifier 300
 bgp confederation peers 300
 neighbor 192.168.1.1 remote-as 100
 neighbor 192.168.2.2 remote-as 300
 !
 address-family ipv4 unicast
  neighbor 192.168.2.2 default-originate
 exit-address-family
!
router isis 1
 is-type level-2-only
 net 49.0001.0002.0002.0002.00
 redistribute ipv4 connected level-2
!
end

router:

!
interface ntfp2
 ip router isis 1
 isis circuit-type level-2-only
!
router bgp 300
 no bgp ebgp-requires-policy
 bgp confederation identifier 300
 bgp confederation peers 200
 neighbor 192.168.2.1 remote-as 200
 neighbor 192.168.3.2 remote-as 400
 !
 address-family ipv4 unicast
  network 3.3.3.0/24
 exit-address-family
!
router isis 1
 is-type level-2-only
 net 49.0001.0003.0003.0003.00
 redistribute ipv4 connected level-2
!
end

on dut result of show bgp ipv4 unicast command is:
show bgp ipv4 unicast

  BGP table version is 1, local router ID is 192.168.2.1, vrf id 0
  Default local pref 100, local AS 200
  Status codes:  s suppressed, d damped, h history, * valid, > best, = multipath,
                 i internal, r RIB-failure, S Stale, R Removed
  Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self
  Origin codes:  i - IGP, e - EGP, ? - incomplete
  RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
  *> 1.1.1.0/24       192.168.1.1              0             0 100 i

instead of

sho bgp ipv4 unicast
BGP table version is 3, local router ID is 192.168.2.1, vrf id 0
Default local pref 100, local AS 200
Status codes:  s suppressed, d damped, h history, * valid, > best, = multipath,
               i internal, r RIB-failure, S Stale, R Removed
Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self
Origin codes:  i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

   Network          Next Hop            Metric LocPrf Weight Path
*> 1.1.1.0/24       192.168.1.1              0             0 100 i
*> 3.3.3.0/24       192.168.2.2              0    100      0 (300) i
*> 4.4.4.0/24       192.168.3.2              0    100      0 (300) 400 i

Displayed  3 routes and 3 total paths

According to RFC 5065:the usage of one of the member AS number as the
confederation identifier is not forbidden.

fixes are the following

in bgp_route.c:
in bgp_update remove the test for presence of confederation id in
as_path since, this case is allowed;

in bgp_vty.c
bgp_confederation_peers, remove the test on peer as value

in bgpd.c
bgp_confederation_peers_add
remove the test on peer as value
invert the order of setting peer->sort value and peer->local_as,
since peer->sort is depending from current peer->local_as value

bgp_confederation_peers_remove
invert the order of setting peer->sort value and peer->local_as,
since peer->sort is depending from current peer->local_as value

Signed-off-by: Francois Dumontet <francois.dumontet@6wind.com>