dkms module is not automatically rebuild when installing new linux-image package

[Impact]
Users of the openvswitch + openvswitch DKMS modules are broken after kernel upgrades without manual intervention. DKMS modules should be auto-rebuilt.

[Test Case]
Install Ubuntu 12.04 (without any kernel updates)
sudo apt-get install openvswitch-datapath-dkms
sudo apt-get install openvswitch-switch
Upgrade to new 3.2 kernel update (or even the new 3.5 kernel for 12.04.2)
Reboot
sudo service openvswitch-switch start
(will fail as DKMS modules not found for new kernel)

[Regression Potential]
The fix for this is minimal (single line) and just impacts the auto-rebuild config for dkms.

However its bundled with the 3.5 kernel compatibility fixes which also remove the _mod suffix from the DKMS built modules. This has the effect that if the DKMS modules are not built openvswitch will fall-back to the less feature-full native openvswitch module provided by the kernel itself (this is aligned to behavior in quantal and raring).

[Original Bug Report]
Hello all,

I've noticed that the openvswitch_mod and brcompat_mod modules are not automatically rebuild when I've upgraded to the latest linux-image-3.2.0-20-generic, thus rendering my openvswitch config unusable after a reboot to said new kernel.

Manual rebuilding and installation worked as expected:
---------------cut---------
root@d02-spi-2:~# uname -a
Linux d02-spi-2 3.2.0-20-generic #32-Ubuntu SMP Thu Mar 22 02:22:46 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux

root@d02-spi-2:~# dpkg -l | egrep 'linux-(image|headers)'
ii linux-headers-3.2.0-19 3.2.0-19.31 Header files related to Linux kernel version 3.2.0
ii linux-headers-3.2.0-19-generic 3.2.0-19.31 Linux kernel headers for version 3.2.0 on 64 bit x86 SMP
ii linux-headers-3.2.0-20 3.2.0-20.32 Header files related to Linux kernel version 3.2.0
ii linux-headers-3.2.0-20-generic 3.2.0-20.32 Linux kernel headers for version 3.2.0 on 64 bit x86 SMP
ii linux-headers-server 3.2.0.20.22 Linux kernel headers on Server Equipment.
ii linux-image-3.2.0-19-generic 3.2.0-19.31 Linux kernel image for version 3.2.0 on 64 bit x86 SMP
ii linux-image-3.2.0-20-generic 3.2.0-20.32 Linux kernel image for version 3.2.0 on 64 bit x86 SMP
ii linux-image-server 3.2.0.20.22 Linux kernel image on Server Equipment.

root@d02-spi-2:~# dkms status -m openvswitch
openvswitch, 1.4.0, 3.2.0-19-generic, x86_64: installed
root@d02-spi-2:~# dkms build -m openvswitch -v 1.4.0

Kernel preparation unnecessary for this kernel. Skipping...

Building module:
cleaning build area....(bad exit status: 2)
./configure --with-linux=/usr/src/linux-headers-3.2.0-20-generic ; make -C datapath/linux..........
cleaning build area....(bad exit status: 2)

DKMS: build completed.
root@d02-spi-2:~# dkms install -m openvswitch -v 1.4.0

openvswitch_mod:
Running module version sanity check.
 - Original module
   - No original module exists within this kernel
 - Installation
   - Installing to /lib/modules/3.2.0-20-generic/updates/dkms/

brcompat_mod.ko:
Running module version sanity check.
 - Original module
   - No original module exists within this kernel
 - Installation
   - Installing to /lib/modules/3.2.0-20-generic/updates/dkms/

depmod......

DKMS: install completed.
root@d02-spi-2:~# dkms status -m openvswitch
openvswitch, 1.4.0, 3.2.0-19-generic, x86_64: installed
openvswitch, 1.4.0, 3.2.0-20-generic, x86_64: installed
---------------cut---------

Regards,
Ralf

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: openvswitch-datapath-dkms 1.4.0-1ubuntu1
ProcVersionSignature: Ubuntu 3.2.0-20.32-generic 3.2.12
Uname: Linux 3.2.0-20-generic x86_64
ApportVersion: 1.94.1-0ubuntu2
Architecture: amd64
Date: Thu Mar 22 14:42:27 2012
PackageArchitecture: all
SourcePackage: openvswitch
UpgradeStatus: No upgrade log present (probably fresh install)