Add image configuration tests

Add image configuration tests

[Bug/Feature]  Integration tests verifying containers' images
               completeness. If the tests fail, the containers will
               most probably not run under SCS.
               The following elements are checked:
                * existence of "security-containers" user with UID
                  of 377
                * existence and correctness of dbus configuration
                  ("security-containers" should be allowed to use
                   "org.tizen.containers.domain" socket)
               The names and paths to the containers' root file
               systems are extracted from SCS daemon and libvirt
               configs (/etc/security-containers/).
[Cause]        N/A
[Solution]     N/A
[Verification] Build, install, run tests (sc_int_tests.py). Check
               various scenarios: remove or corrupt dbus config
               (etc/dbus-1/system.d/org.tizen.containers.domain.conf)
               or libvirt's XML config, remove "security-containers"
               user inside a container, change it's UID, etc.

Change-Id: I69782f348ecb1c6b63a60286a3a8ee4ae3f8465b
Signed-off-by: Michal Witanowski <m.witanowski@samsung.com>