Proper switching focus between containers without freezing background ones

Proper switching focus between containers without freezing background ones

[Bug/Feature]   The current focus switching was freezing all
                background containers
[Cause]         N/A
[Solution]      The idea is that a background container should be able to
                respond to messages/notifications. It cannot be frozen.
                At least not completely (user applications might, system
                daemons/services shouldn't). This change starts the
                foundations for such operations:
                - added functions for settings and getting scheduler
                  options for CFS scheduler using libvirt API
                - some cleanups in ContainerAdmin class
                - removal of getAdmin() and new API for the Container class
                - new tests for all the new functionalities
                - restructurization of config files for unit_tests
                  (one directory of configs per class)
                - removal of "config" in: /etc/security-containers/config/
[Verification]  Build, install, run tests on host, build RPM

Change-Id: I2288b71632a6c8043fe47244fa9c0754241cba88
Signed-off-by: Lukasz Pawelczyk <l.pawelczyk@partner.samsung.com>