Support Leader Election for GLBC for HA masters

[freehan]

GLBC should be leader-elected, (the same way we are doing for scheduler, controller-manager, cluster-autoscaler, etc.)
As an example, this is what scheduler is doing:
https://github.com/kubernetes/kubernetes/blob/master/cmd/kube-scheduler/app/server.go#L414

[rramkumar1]

/assign @nicksardo

[rramkumar1]

Fixed by #258
/close