virt: Cartesian config update v3. with exclude filter RFC

***Pull-request is based on virt: Cartesian config update v3. After pulling this pull-request there will only stay 2 commit of 10.

repaired indentation problems which were commented in https://github.com/autotest/virt-test/pull/252

Features:

    virt: Adds possibility to exclude filter from config.

Unittest:

    virt: Extends Cartesian config unittests for new features
        and replace exec call by better version