The client-go signature for most methods adds a context.Context
object, and also makes Options mandatory. Feed through a
context.Context through many of our methods (but use context.TODO to
stop it getting totally out of hand!)
We don't call klog.InitFlags yet, because that will cause a flag
redefinition error until we get everyone to stop using glog. That
will happen when we update to k8s 1.13.