pkg/kubelet/nodeshutdown/systemd: fix for dbus 5.0.4

dbus 5.0.4 adds StoreProperty method which needs to be implemented for
the mock.

Fixes the errors like

> pkg/kubelet/nodeshutdown/systemd/inhibit_linux_test.go:88:9: cannot use f.fakeDBusObject (variable of type *fakeDBusObject) as dbus.BusObject value in return statement: missing method StoreProperty

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

pkg/kubelet/nodeshutdown/systemd/inhibit_linux_test.go

@@ -71,6 +71,10 @@ func (obj *fakeDBusObject) SetProperty(p string, v interface{}) error {
 	return nil
 }
 
+func (obj *fakeDBusObject) StoreProperty(p string, v interface{}) error {
+	return nil
+}
+
 func (obj *fakeDBusObject) Destination() string {
 	return ""
 }