Use upstart for ddclient daemon management

As ddclient stop init.d is not working in all cases.

This avoids multiple ddclient daemon instances with memory and CPU consumption.
Added migration script to stop ddclient instances from init.d script

And do what enableActions do
Added defensive code to avoid leaving broken packages

Using silentRoot
Merge pull request #567 from Zentyal/ejhernandez/ddclient-upstart

Use upstart for ddclient daemon management