[VOL-1866] Changed module dependency to v12.0.0 of k8s client-go and v1.15.4 of k8s api/apimachinery in sync with other voltha components

Had to use pseudo-version corresponding to v12.0.0 of k8s client-go
because golang proxy is no longer serving the modules not complying
to Semantic Import Versioning rules including client-go v12.0.0.
Refer to https://github.com/kubernetes/client-go/issues/631 and
https://github.com/golang/go/issues/33558

Change-Id: I2e558bab7f0702f230761319eb5392a7d0532ea3
diff --git a/vendor/k8s.io/api/networking/v1/generated.proto b/vendor/k8s.io/api/networking/v1/generated.proto
index ab3731e..cbbb265 100644
--- a/vendor/k8s.io/api/networking/v1/generated.proto
+++ b/vendor/k8s.io/api/networking/v1/generated.proto
@@ -48,7 +48,7 @@
 // NetworkPolicy describes what network traffic is allowed for a set of Pods
 message NetworkPolicy {
   // Standard object's metadata.
-  // More info: https://git.k8s.io/community/contributors/devel/api-conventions.md#metadata
+  // More info: https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#metadata
   // +optional
   optional k8s.io.apimachinery.pkg.apis.meta.v1.ObjectMeta metadata = 1;
 
@@ -101,7 +101,7 @@
 // NetworkPolicyList is a list of NetworkPolicy objects.
 message NetworkPolicyList {
   // Standard list metadata.
-  // More info: https://git.k8s.io/community/contributors/devel/api-conventions.md#metadata
+  // More info: https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#metadata
   // +optional
   optional k8s.io.apimachinery.pkg.apis.meta.v1.ListMeta metadata = 1;
 
@@ -180,7 +180,7 @@
   repeated NetworkPolicyEgressRule egress = 3;
 
   // List of rule types that the NetworkPolicy relates to.
-  // Valid options are Ingress, Egress, or Ingress,Egress.
+  // Valid options are "Ingress", "Egress", or "Ingress,Egress".
   // If this field is not specified, it will default based on the existence of Ingress or Egress rules;
   // policies that contain an Egress section are assumed to affect Egress, and all policies
   // (whether or not they contain an Ingress section) are assumed to affect Ingress.