debian: Make DKMS automatically build for running kernel.

debian: Make DKMS automatically build for running kernel.

By default DKMS doesn't build on demand for each kernel booted or updated.
Adding AUTOINSTALL=yes gives it this behavior.  Based on a small sample of
Debian packages and how-to guides for Ubuntu, AUTOINSTALL=yes is what most
packages use and what users expect.

Fix-suggested-by: Kirill Kabardin
Reported-by: Ralf Heiringhoff <ralf@frosty-geek.net>
Reported-at: https://bugs.launchpad.net/bugs/962189
Signed-off-by: Ben Pfaff <blp@nicira.com>