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/jcmturner/gokrb5.v7/config/error.go b/demo_test/vendor/gopkg.in/jcmturner/gokrb5.v7/config/error.go
new file mode 100644
index 0000000..1fbda51
--- /dev/null
+++ b/demo_test/vendor/gopkg.in/jcmturner/gokrb5.v7/config/error.go
@@ -0,0 +1,30 @@
+package config
+
+import "fmt"
+
+// UnsupportedDirective error.
+type UnsupportedDirective struct {
+	text string
+}
+
+// Error implements the error interface for unsupported directives.
+func (e UnsupportedDirective) Error() string {
+	return e.text
+}
+
+// Invalid config error.
+type Invalid struct {
+	text string
+}
+
+// Error implements the error interface for invalid config error.
+func (e Invalid) Error() string {
+	return e.text
+}
+
+// InvalidErrorf creates a new Invalid error.
+func InvalidErrorf(format string, a ...interface{}) Invalid {
+	return Invalid{
+		text: fmt.Sprintf("invalid krb5 config "+format, a...),
+	}
+}