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/github.com/rcrowley/go-metrics/metrics.go b/demo_test/vendor/github.com/rcrowley/go-metrics/metrics.go
new file mode 100644
index 0000000..b97a49e
--- /dev/null
+++ b/demo_test/vendor/github.com/rcrowley/go-metrics/metrics.go
@@ -0,0 +1,13 @@
+// Go port of Coda Hale's Metrics library
+//
+// <https://github.com/rcrowley/go-metrics>
+//
+// Coda Hale's original work: <https://github.com/codahale/metrics>
+package metrics
+
+// UseNilMetrics is checked by the constructor functions for all of the
+// standard metrics.  If it is true, the metric returned is a stub.
+//
+// This global kill-switch helps quantify the observer effect and makes
+// for less cluttered pprof profiles.
+var UseNilMetrics bool = false