bgpd: Validate imported routes next-hop that is in a default VRF

Without this patch:

```
r1# sh ip bgp vrf CUSTOMER-A
BGP table version is 1, local router ID is 20.20.20.0, vrf id 4
Default local pref 100, local AS 65000
Status codes:  s suppressed, d damped, h history, u unsorted, * 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
     192.168.2.0/24   192.168.179.5@0<
                                             0             0 479 ?

Displayed 1 routes and 1 total paths
r1#
```

This is because the route is imported, next-hop is in a default VRF, and we should
evaluate an ultimate path info, not the current path info.

After:

```
r1# sh ip bgp vrf CUSTOMER-A
BGP table version is 1, local router ID is 20.20.20.0, vrf id 4
Default local pref 100, local AS 65000
Status codes:  s suppressed, d damped, h history, u unsorted, * 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
 *>  192.168.2.0/24   192.168.179.5@0<
                                             0             0 479 ?

Displayed 1 routes and 1 total paths
r1#
```

In both cases next-hop in cache table is valid:

```
r1# sh ip bgp nexthop
Current BGP nexthop cache:
 192.168.179.5 valid [IGP metric 0], #paths 2, peer 192.168.179.5
  Resolved prefix 192.168.179.0/24
  if r1-eth0
  Last update: Thu Sep  5 11:24:37 2024
r1#
```

Signed-off-by: Donatas Abraitis <donatas@opensourcerouting.org>

0 files changed, 0 insertions, 0 deletions