Tweak event defer example
Tweak event defer example

Enable defer source in time callback instead of in defer callback. Doint it
in the defer callback prevents the event loop from going to sleep and just
repeatedly calls the defer callback (until exit).

Also use explicit counter instead of event iteration since it is not
that intuitive what iteration we are on. Each dispatch of a time or defer
source is one iteration. That is each time the time source is dispatched
we increase with 2 (since the defer source is also dispatched).

martin-ejdestig/systemdcpp,martin-ejdestig/systemdcpp