zebra: Fix missing VRF flag

When `ip link del vrf1`, `zebra` have wrongly forgot it is a vrf type.
It thought it is a normal interface.

```
ZEBRA: [KMXEB-K771Y] netlink_parse_info: netlink-listen (NS 0) type RTM_DELLINK(17), len=588, seq=0, pid=0
ZEBRA: [TDJW2-B9KJW] RTM_DELLINK for vrf1(148) <- Wrongly regarded as normal interface
ZEBRA: [ZRQ6P-Y3WVQ] PIM: [W6DJA-XRCK3] PIM INTERFACE DOWN: on interface vrf1: link down
```

It triggers problems on clients.

It will kept as an normal interface in 'show run' after even completely removed,
as said in PR#13388. The clients will accept this wrong interface as normal,
not vrf type:

```
interface vrf1
exit
```
Or

```
interface vrf1
 ip ospf network broadcast
exit
```

The root cause is that the `ifp->status`'s `ZEBRA_INTERFACE_VRF_LOOPBACK`
flag of this vrf is cleared too early. After that clear, `zebra` ( and
then clients ) will take it as normal interface. So, move it from "vrf1"
to "default" VRF, then an unexpected interface is created.

So, put the deletion of this flag at the last.

Signed-off-by: anlan_cs <[email protected]>

zebra/if_netlink.c

@@ -2323,8 +2323,6 @@ int netlink_link_change(struct nlmsghdr *h, ns_id_t ns_id, int startup)
 			zlog_debug("RTM_DELLINK for %s(%u)", name,
 				   ifp->ifindex);
 
-		UNSET_FLAG(ifp->status, ZEBRA_INTERFACE_VRF_LOOPBACK);
-
 		if (IS_ZEBRA_IF_BOND(ifp))
 			zebra_l2if_update_bond(ifp, false);
 		if (IS_ZEBRA_IF_BOND_SLAVE(ifp))

zebra/interface.c

@@ -800,6 +800,8 @@ void if_delete_update(struct interface **pifp)
 	if (ifp->vrf->vrf_id && !vrf_is_backend_netns())
 		if_handle_vrf_change(ifp, VRF_DEFAULT);
 
+	UNSET_FLAG(ifp->status, ZEBRA_INTERFACE_VRF_LOOPBACK);
+
 	/* Reset some zebra interface params to default values. */
 	zif = ifp->info;
 	if (zif) {