debian: Dont fail init if module cant be inserted

debian: Dont fail init if module cant be inserted

The problem here is that the daemon is started/restarted on
package installation, but the module may not be present at that
time and (as far as I know) its bad form to fail the package installation
in that circumstance.

In keeping with the way ipvsadm handles a similar problem,
exit with a non-error exit status if the module can't be inserted.
The loud error message is still displayed.

Signed-off-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Ben Pfaff <blp@nicira.com>