[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/authentication/v1/types_swagger_doc_generated.go b/vendor/k8s.io/api/authentication/v1/types_swagger_doc_generated.go
index f2c9b95..09f6b92 100644
--- a/vendor/k8s.io/api/authentication/v1/types_swagger_doc_generated.go
+++ b/vendor/k8s.io/api/authentication/v1/types_swagger_doc_generated.go
@@ -51,7 +51,7 @@
 	"":                  "TokenRequestSpec contains client provided parameters of a token request.",
 	"audiences":         "Audiences are the intendend audiences of the token. A recipient of a token must identitfy themself with an identifier in the list of audiences of the token, and otherwise should reject the token. A token issued for multiple audiences may be used to authenticate against any of the audiences listed but implies a high degree of trust between the target audiences.",
 	"expirationSeconds": "ExpirationSeconds is the requested duration of validity of the request. The token issuer may return a token with a different validity duration so a client needs to check the 'expiration' field in a response.",
-	"boundObjectRef":    "BoundObjectRef is a reference to an object that the token will be bound to. The token will only be valid for as long as the bound objet exists.",
+	"boundObjectRef":    "BoundObjectRef is a reference to an object that the token will be bound to. The token will only be valid for as long as the bound object exists. NOTE: The API server's TokenReview endpoint will validate the BoundObjectRef, but other audiences may not. Keep ExpirationSeconds small if you want prompt revocation.",
 }
 
 func (TokenRequestSpec) SwaggerDoc() map[string]string {