After tethering switch-off the firewall is no longer active

```
What steps will reproduce the problem?
1.enable droidwall (I use whitelist mode)
1.enable tethering (PC tethered to the phone over wifi, inet reached via 3G)
2.tethering ok and the local firewall seem ok too (from the status menu the
droidwall chain has 1 reference)
3.disable tethering -> after this no more references to the droidwall chain and
all applications on the phone get access to the 3G interface

What is the expected output? What do you see instead?
the expected behaviour should intercept the tethering off event and restore the
droidwall iptables setup (the tethering itself uses iptables and probably the
tethering switch-off flushes the tables)

What version of the product are you using? On what operating system?
droidwall 1.5.2 and 1.5.4, Nexus S (rooted) with stock gingerbread 2.3.4 and
cyanogenmod 7.1

Please provide any additional information below.

```

Original issue reported on code.google.com by `g.agu...@gmail.com` on 26 Nov 2011 at 5:40