selftest: Introduce scenario_test

This covers some unit tests for scenario module (Scenario class).

Change-Id: I4c80047bb03ae8254c192057007fa7df84478605
diff --git a/selftest/scenario_test/scenario_case_03@specific.conf b/selftest/scenario_test/scenario_case_03@specific.conf
new file mode 100644
index 0000000..925f908
--- /dev/null
+++ b/selftest/scenario_test/scenario_case_03@specific.conf
@@ -0,0 +1,2 @@
+somelist:
+- somelistitem: 'specific'