call dpkg with --no-triggers by default

Implemented a long while ago now with relatively good progress reporting
involving triggers is a good time to try delaying the execution of
triggers across dpkg invocations finally by default.

Note: The bugreport talks also about 'smarter' configuration which is a
much bigger part and approached from multiple directions, but doesn't
really involve triggers per-se so considering it decoupled should help
in getting it done…

Closes: #626599