plugins: log -- Implement basic functionality

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
plugin: std -- Add args specification

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
test: Update simple

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>