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/google.golang.org/grpc/go.mod b/demo_test/vendor/google.golang.org/grpc/go.mod
new file mode 100644
index 0000000..ecef1ab
--- /dev/null
+++ b/demo_test/vendor/google.golang.org/grpc/go.mod
@@ -0,0 +1,16 @@
+module google.golang.org/grpc
+
+go 1.11
+
+require (
+	github.com/cncf/udpa/go v0.0.0-20191209042840-269d4d468f6f
+	github.com/envoyproxy/go-control-plane v0.9.4
+	github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b
+	github.com/golang/mock v1.1.1
+	github.com/golang/protobuf v1.3.3
+	github.com/google/go-cmp v0.2.0
+	golang.org/x/net v0.0.0-20190311183353-d8887717615a
+	golang.org/x/oauth2 v0.0.0-20180821212333-d2e6202438be
+	golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a
+	google.golang.org/genproto v0.0.0-20190819201941-24fa4b261c55
+)