Switch to github.com/coreos/go-systemd/v22 and drop older package

- We use the new v22 module released on May 10
- We drop the unmaintained `github.com/coreos/pkg`

Signed-off-by: Davanum Srinivas <davanum@gmail.com>

staging/src/k8s.io/apiserver/go.mod

@@ -7,7 +7,7 @@ go 1.16
 require (
 	github.com/NYTimes/gziphandler v1.1.1 // indirect
 	github.com/coreos/go-oidc v2.1.0+incompatible
-	github.com/coreos/go-systemd v0.0.0-20190321100706-95778dfbb74e
+	github.com/coreos/go-systemd/v22 v22.3.2
 	github.com/davecgh/go-spew v1.1.1
 	github.com/emicklei/go-restful v2.9.5+incompatible
 	github.com/evanphx/json-patch v4.11.0+incompatible

staging/src/k8s.io/apiserver/pkg/server/genericapiserver.go

@@ -24,7 +24,7 @@ import (
 	"sync"
 	"time"
 
-	systemd "github.com/coreos/go-systemd/daemon"
+	systemd "github.com/coreos/go-systemd/v22/daemon"
 
 	"k8s.io/apimachinery/pkg/api/meta"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"