[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 kubernetes/client-go#631 and
golang/go#33558

Change-Id: I2e558bab7f0702f230761319eb5392a7d0532ea3

Author: gkumar78

go.mod

@@ -8,20 +8,14 @@ require (
 	github.com/gogo/protobuf v1.2.1 // indirect
 	github.com/golang/protobuf v1.3.1
 	github.com/golang/snappy v0.0.1 // indirect
-	github.com/google/btree v1.0.0 // indirect
-	github.com/google/gofuzz v0.0.0-20170612174753-24818f796faf // indirect
 	github.com/google/uuid v1.1.1
 	github.com/googleapis/gnostic v0.2.0 // indirect
-	github.com/gregjones/httpcache v0.0.0-20190212212710-3befbb6ad0cc // indirect
 	github.com/imdario/mergo v0.3.7 // indirect
 	github.com/json-iterator/go v1.1.6 // indirect
-	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
-	github.com/modern-go/reflect2 v0.0.0-20180701023420-4b7aa43c6742 // indirect
 	github.com/onsi/ginkgo v1.10.2 // indirect
 	github.com/onsi/gomega v1.7.0 // indirect
 	github.com/opencord/voltha-go v2.2.0+incompatible
 	github.com/opencord/voltha-protos v1.0.3
-	github.com/peterbourgon/diskv v2.0.1+incompatible // indirect
 	github.com/pkg/errors v0.8.1 // indirect
 	github.com/spf13/pflag v1.0.3 // indirect
 	github.com/stretchr/testify v1.3.0
@@ -30,17 +24,13 @@ require (
 	go.uber.org/zap v1.9.1 // indirect
 	golang.org/x/crypto v0.0.0-20190320223903-b7391e95e576 // indirect
 	golang.org/x/net v0.0.0-20190322120337-addf6b3196f6
-	golang.org/x/oauth2 v0.0.0-20190319182350-c85d3e98c914 // indirect
 	golang.org/x/sys v0.0.0-20190322080309-f49334f85ddc // indirect
 	golang.org/x/time v0.0.0-20190308202827-9d24e82272b4 // indirect
-	google.golang.org/appengine v1.5.0 // indirect
 	google.golang.org/genproto v0.0.0-20190321212433-e79c0c59cdb5 // indirect
 	google.golang.org/grpc v1.19.1
 	gopkg.in/inf.v0 v0.9.1 // indirect
 	gopkg.in/yaml.v2 v2.2.2 // indirect
-	k8s.io/api v0.0.0-20190222213804-5cb15d344471
-	k8s.io/apimachinery v0.0.0-20190322104434-6d73c65dcf6c
-	k8s.io/client-go v10.0.0+incompatible
-	k8s.io/klog v0.2.0 // indirect
-	sigs.k8s.io/yaml v1.1.0 // indirect
+	k8s.io/api v0.0.0-20190620084959-7cf5895f2711
+	k8s.io/apimachinery v0.0.0-20190612205821-1799e75a0719
+	k8s.io/client-go v0.0.0-20190620085101-78d2af792bab // pseudo version corresponding to v12.0.0
 )