tests: add OSCI test definition
    
    Add very basic libreswan server based integration tests:
     * basic connect with 2 minutes stability check
     * ikev1/ikev2
     * terminating libreswan service
     * DNS pull
    
    Using these tests from NM repo:
     * libreswan_add_profile
     * libreswan_connection_renewal
     * libreswan_main
     * libreswan_activate_asking_for_password_and_secret
     * libreswan_delete_active_profile
     * libreswan_dns
    
    NM repo:
     https://gitlab.freedesktop.org/NetworkManager/NetworkManager-ci/blob/master/nmcli/features/libreswan.feature