Description of problem:
Set openshift_ansible_vars openshift_node_kubelet_args with some feature gates.
After installation completed, node config does not have the feature gates we set (It works in this way in OCP 3.9).

Version-Release number of the following components:
rpm -q openshift-ansible
openshift-ansible-3.10.0-0.54.0.git.0.537c485.el7.noarch.rpm
ansible --version
2.4.4.0-1.el7ae

How reproducible:
Always

Steps to Reproduce:
1.Set openshift_ansible_vars
  osm_api_server_args: '{"feature-gates": ["MountPropagation=true", "ExpandPersistentVolumes=true", "PersistentLocalVolumes=true", "BlockVolume=true"]}'
  osm_controller_args: '{"feature-gates": ["MountPropagation=true", "ExpandPersistentVolumes=true", "VolumeScheduling=true", "PersistentLocalVolumes=true", "BlockVolume=true"]}'
  openshift_master_scheduler_args: '{"feature-gates": ["VolumeScheduling=true"]}'
  openshift_master_admission_plugin_config: '{"PersistentVolumeClaimResize":{"configuration":{"apiVersion":"v1", "kind":"DefaultAdmissionConfig", "disable":false}}}'
  openshift_node_kubelet_args: '{"feature-gates": ["MountPropagation=true", "ExpandPersistentVolumes=true", "PersistentLocalVolumes=true", "BlockVolume=true"]}'
2.Wait for the installtion to completed.
3.Check master and node config.

Actual results:
# grep -i -r feature /etc/origin/master/ -A5
/etc/origin/master/master-config.yaml:    feature-gates:
/etc/origin/master/master-config.yaml-    - MountPropagation=true
/etc/origin/master/master-config.yaml-    - ExpandPersistentVolumes=true
/etc/origin/master/master-config.yaml-    - PersistentLocalVolumes=true
/etc/origin/master/master-config.yaml-    - BlockVolume=true
/etc/origin/master/master-config.yaml-    storage-backend:

# grep -i -r feature /etc/origin/node/ -A2
/etc/origin/node/bootstrap-node-config.yaml:  feature-gates:
/etc/origin/node/bootstrap-node-config.yaml-  - RotateKubeletClientCertificate=true,RotateKubeletServerCertificate=true
/etc/origin/node/bootstrap-node-config.yaml-  rotate-certificates:


Expected results:
Node config should contain proper feature gates as we set.

Additional info: