Bug 8231

I ran into a crash trying to run "ip addr list" in a docker container running busybox from https://registry.hub.docker.com/_/busybox/:

```
mak@trinity10:~$ docker run --publish-service srvC.net1.calico --name c-C -ti busybox:latest sh
/ # busybox 
BusyBox v1.22.1 (2014-05-22 23:22:11 UTC) multi-call binary.
...

/ # ifconfig
cali0     Link encap:Ethernet  HWaddr EE:EE:EE:EE:EE:EE  
          inet addr:192.168.89.20  Bcast:0.0.0.0  Mask:255.255.255.255
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:7 errors:0 dropped:0 overruns:0 frame:0
          TX packets:8 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:738 (738.0 B)  TX bytes:648 (648.0 B)

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

/ # ip addr list
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default 
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
Segmentation fault
```

See also https://github.com/Metaswitch/calico-docker/issues/4