bfdd: Fix malformed session with vrf

bfdd: Fix malformed session with vrf

With this configuration:

```
bfd
 peer 33:33::66 local-address 33:33::88 vrf vrf8 interface enp1s0
 exit
 !
exit
```

The bfd session can't be established with error:

```
bfdd[18663]: [YA0Q5-C0BPV] control-packet: wrong vrfid. [mhop:no peer:33:33::66 local:33:33::88 port:2 vrf:61]
```

The vrf check should use the carefully adjusted `vrfid`, which is
based on globally/reliable interface.  We can't believe the
`bvrf->vrf->vrf_id` because the `/proc/sys/net/ipv4/udp_l3mdev_accept`
maybe is set "1" in VRF-lite backend even with security drawback.

Just correct the vrf check.

Signed-off-by: anlan_cs <vic.lan@pica8.com>