SEBA-902 single-olt tests;
Pin protoc-gen-go to 1.3.2 to resolve compatibility issue;
Run go mod tidy / go mod vendor on importer;
Add Go Module support to demotest

Change-Id: Ifde824fc9a6317b0adc1e12bea54ee1f9b788906
diff --git a/demo_test/vendor/gopkg.in/yaml.v2/go.mod b/demo_test/vendor/gopkg.in/yaml.v2/go.mod
new file mode 100644
index 0000000..1934e87
--- /dev/null
+++ b/demo_test/vendor/gopkg.in/yaml.v2/go.mod
@@ -0,0 +1,5 @@
+module "gopkg.in/yaml.v2"
+
+require (
+	"gopkg.in/check.v1" v0.0.0-20161208181325-20d25e280405
+)