Set leader-elect for kube-scheduler to true

Thanks to some great sleuthing by ikruglov!

kube-controller-manager defaults --leader-elect to true. We should
do the same for kube-scheduler. kube-scheduler used to have this
set to true, but it got lost during refactoring in:
efb2bb71cd

cmd/kube-controller-manager/app/options/options.go

@@ -60,7 +60,6 @@ func NewKubeControllerManagerOptions() *KubeControllerManagerOptions {
 		gcIgnoredResources = append(gcIgnoredResources, componentconfig.GroupResource{Group: r.Group, Resource: r.Resource})
 	}
 	s.Generic.ComponentConfig.GCIgnoredResources = gcIgnoredResources
-	s.Generic.ComponentConfig.LeaderElection.LeaderElect = true
 
 	return &s
 }