Description of problem:
when delete a kubeletconfig ,return time is too long(nearly 10 minutes)

Version-Release number of selected component (if applicable):
4.0.0-0.nightly-2019-03-04-234414
oc v4.0.0-0.182.0

How reproducible:
always

Steps to Reproduce:
1.edit machineconfigpool worker, add label"custom-kubelet: max-pods-worker"
#oc edit machineconfigpool worker
for example:
metadata:
  creationTimestamp: 2019-03-07T07:10:04Z
  generation: 1
  labels:
    custom-kubelet: max-pods-worker(add this line)
  ...

2.create a kubeletconfig cr
oc create -f worker-kube-config.yaml
yaml file as:
apiVersion: machineconfiguration.openshift.io/v1
kind: KubeletConfig
metadata:
  name: set-max-pods-worker
spec:
  machineConfigPoolSelector:
    matchLabels:
      custom-kubelet: max-pods-worker
  kubeletConfig:
    maxPods: 249

3.oc get machineconfig
generate a new machineconfig named "99-worker-74b4fa0b-4091-11e9-96ec-067bf345463e-kubelet"

4.login all worker node, check /etc/kubernetes/kubelet.conf has the kubelet configuration "maxPods: 249"

5.oc delete kubeletconfig set-max-pods-worker


Actual results:
5.show message "kubeletconfig.machineconfiguration.openshift.io "set-max-pods-worker" deleted", and return time of this command is nearly 10 minutes.

Expected results:
show message "kubeletconfig.machineconfiguration.openshift.io "set-max-pods-worker" deleted", and return immediately


Additional info:
when take step 5, check machineconfig in another terminal，the 99-worker-74b4fa0b-4091-11e9-96ec-067bf345463e-kubelet disappear immediately.


#oc logs machine-config-controller-8cc654f5d-rlckl -n openshift-machine-config-operator | grep set-max-pods-worker
error log:
I0307 09:45:50.893105       1 kubelet_config_controller.go:412] Applied KubeletConfig set-max-pods-worker on MachineConfigPool worker
I0307 09:45:51.048254       1 kubelet_config_controller.go:245] Error syncing kubeletconfig set-max-pods-worker: Operation cannot be fulfilled on kubeletconfigs.machineconfiguration.openshift.io "set-max-pods-worker": the object has been modified; please apply your changes to the latest version and try again
I0307 09:45:51.698293       1 kubelet_config_controller.go:412] Applied KubeletConfig set-max-pods-worker on MachineConfigPool worker
E0307 09:45:51.859637       1 kubelet_config_controller.go:250] Operation cannot be fulfilled on kubeletconfigs.machineconfiguration.openshift.io "set-max-pods-worker": the object has been modified; please apply your changes to the latest version and try again
I0307 09:45:51.859670       1 kubelet_config_controller.go:251] Dropping kubeletconfig "set-max-pods-worker" out of the queue: Operation cannot be fulfilled on kubeletconfigs.machineconfiguration.openshift.io "set-max-pods-worker": the object has been modified; please apply your changes to the latest version and try again
I0307 09:45:52.500112       1 kubelet_config_controller.go:412] Applied KubeletConfig set-max-pods-worker on MachineConfigPool worker
I0307 09:45:52.648116       1 kubelet_config_controller.go:245] Error syncing kubeletconfig set-max-pods-worker: Operation cannot be fulfilled on kubeletconfigs.machineconfiguration.openshift.io "set-max-pods-worker": the object has been modified; please apply your changes to the latest version and try again
I0307 09:45:53.292696       1 kubelet_config_controller.go:412] Applied KubeletConfig set-max-pods-worker on MachineConfigPool worker
I0307 09:45:53.455527       1 kubelet_config_controller.go:245] Error syncing kubeletconfig set-max-pods-worker: Operation cannot be fulfilled on kubeletconfigs.machineconfiguration.openshift.io "set-max-pods-worker": the object has been modified; please apply your changes to the latest version and try again