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.
This auto implements the new methods (they panic if called). Technique
borrowed from mockelb (thanks @vainu-arto ).
Assuming this approach works, we can get rid of the annoying
unimplemented.go files.