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/vendor/gopkg.in/jcmturner/gokrb5.v7/credentials/credentials.go b/vendor/gopkg.in/jcmturner/gokrb5.v7/credentials/credentials.go
index 62acab7..beec066 100644
--- a/vendor/gopkg.in/jcmturner/gokrb5.v7/credentials/credentials.go
+++ b/vendor/gopkg.in/jcmturner/gokrb5.v7/credentials/credentials.go
@@ -288,6 +288,11 @@
 	return false
 }
 
+// ValidUntil returns the credential's valid until date
+func (c *Credentials) ValidUntil() time.Time {
+	return c.validUntil
+}
+
 // Attributes returns the Credentials' attributes map.
 func (c *Credentials) Attributes() map[string]interface{} {
 	return c.attributes