Fix Debian procedure for Nova

It's looking like sections which I have intentionally removed
from the Debian procedure made their way in again. This patch
removes them since they are handled by Debconf and make it
unecessarily complicated.

This is a backport of: https://review.openstack.org/97156/

Change-Id: I2750aac023ace124d34fccd664603477b466026f
Merge "Fix Debian procedure for Nova" into stable/icehouse