make ifconfig print vnetids in hex too

[David Gwynne]

so things will look like this:

vlan9: flags=8002<BROADCAST,MULTICAST> mtu 1500
        lladdr 00:00:00:00:00:00
        index 11 priority 0 llprio 3
        vlan: 70 parent interface: <none>
        vnetid: 70 (0x46)
        parent: none
        groups: vlan
        status: no carrier
vxlan0: flags=8802<BROADCAST,SIMPLEX,MULTICAST> mtu 1500
        lladdr fe:e1:ba:d0:40:78
        index 12 priority 0 llprio 3
        vnetid: 4096 (0x1000)
        groups: vxlan
        media: Ethernet autoselect
        status: active

some tools display "vnetids" as hex, so itd be nice to line them
up with ifconfig output a bit easier.

Index: sbin/ifconfig/ifconfig.c
===================================================================
RCS file: /cvs/src/sbin/ifconfig/ifconfig.c,v
retrieving revision 1.334
diff -u -p -r1.334 ifconfig.c
--- sbin/ifconfig/ifconfig.c    13 Dec 2016 01:36:21 -0000      1.334
+++ sbin/ifconfig/ifconfig.c    13 Dec 2016 07:01:33 -0000
@@ -3664,7 +3664,7 @@ getvnetid(void)
                return;
        }
 
-       printf("\tvnetid: %lld\n", ifr.ifr_vnetid);
+       printf("\tvnetid: %lld (0x%llx)\n", ifr.ifr_vnetid, ifr.ifr_vnetid);
 }
 
 void