debian maintainer script refactoring

This commit handle a little bug on packages un-install (if two contrail
package are installed on the same node).
Install and remove are now also standardized, and a missing rm script for
contrail-dns was added.

Change-Id: I57181aa3f36e67d8d6778ce31bdf3cc366f8dbbc
Merge "debian maintainer script refactoring"