kbase: debuglogs: Add a 'TL;DR' section for enabling logging in most common case

kbase: debuglogs: Add a 'TL;DR' section for enabling logging in most common case

The document grew a bit too much explaining all the mistakes we've seen
the users do when configuring logging. Add a section distilling the
configuration of the most basic scenario which we can refer to when
upstream issues are reported. The scenario is for a runtime setting of
logging into a file applied to the 'virtqemud' daemon.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>