Fixes #5845: Add portable init services handling in the Techniques

Ticket: http://www.rudder-project.org/redmine/issues/5845

To be merged in 3.0
Careful! These two lines implemented a clever "frequency limit". By defining persistent classes, and not running the promise again if they are defined, we effectively used a lock (but we can't use locks since we have to nuke cf_lock.db all the time because of the ghastly CFEngine 3.5 version...).

You can just add the same lines to the methods promise above.