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.
We delete old AWS LaunchConfigurations when we see that we have more
than 3. We add a feature flag KeepLaunchConfigurations to disable this
functionality, for backwards compatability.
Fixes#329