Specifics for Debian in Ceilometer

This patch adds Debian specifics for the use of Debconf,
and removes the unwanted parts of the manual that are
automatically configured in the Debian package.

backport: havana
Change-Id: I40e2a17cdc6fa7f5ff4468a2e75e2302c902c7b2
(cherry picked from commit df37e69d774b458dae431b92ded13b45e703267b)
Merge "Specifics for Debian in Ceilometer" into stable/havana