expose causes network overlap complaint on restart

[rade]

$ weave launch
$ weave expose
10.128.0.2
$ route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.1.254   0.0.0.0         UG    0      0        0 wlan0
10.128.0.0      0.0.0.0         255.192.0.0     U     0      0        0 weave
172.17.0.0      0.0.0.0         255.255.0.0     U     0      0        0 docker0
192.168.1.0     0.0.0.0         255.255.255.0   U     9      0        0 wlan0
192.168.48.0    0.0.0.0         255.255.255.0   U     0      0        0 vboxnet0
$ weave stop
$ weave launch
Network 10.128.0.0/10 overlaps with existing route 10.128.0.0/10 on host.
Default -iprange 10.128.0.0/10 overlaps with existing route on host.
Please pick another range and set it on all hosts.

Perhaps we should ignore the weave bridge in our overlap calculations.