Bug 28717: Fix additional content logs

Bug 28717: Fix additional content logs

The logging for additional contents added by bug 26205 has been broken
by but 22544.

This patch is a revisited version as bug 24387 has been pushed.
It does not log MODIFY if no modification has been made on a template
(useful when only 1 version/lang of a content has been modified)

Test plan:
Turn on NewsLog
Add/modify and delete additional contents/News and confirm that
modification are logged.

Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>