AppArmor DBus rules for AkonadiServer

Summary: When I build and install Akonadi (branch release/20.04) on Kubuntu 20.04, server was not able to start, because AppArmor denied access to DBus. I am not expert on AppArmor, but with these modifications, Akonadi is able to run.

Test Plan:
- build install Akonadi on distribution with AppArmor (for example Kubuntu 20.04)
- start akonadi without applied patch, it should fail
- with this patch, it should run properly

Reviewers: knauss

Reviewed By: knauss

Subscribers: dvratil, knauss, kde-pim

Tags: #kde_pim

Differential Revision: https://phabricator.kde.org/D29030