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>

test/e2e_node/docker_util.go

@@ -21,7 +21,7 @@ import (
 	"strings"
 
 	"github.com/blang/semver"
-	systemdutil "github.com/coreos/go-systemd/util"
+	systemdutil "github.com/coreos/go-systemd/v22/util"
 )
 
 // getDockerAPIVersion returns the Docker's API version.