Description of problem:
Upgrade ocp v3.9 to v3.10. A admission plugin config in master-config.yaml has been removed after upgrade. 

On v3.10 master hosts which upgraded from v3.9
# diff pre.cfg post.cfg 
26,30d25
<     PodPreset:
<       configuration:
<         apiVersion: v1
<         disable: false
<         kind: DefaultAdmissionConfig

# cat /tmp/pre.cfg |grep -A 5 PodPreset
    PodPreset:
      configuration:
        apiVersion: v1
        disable: false
        kind: DefaultAdmissionConfig
    RunOnceDuration:
# cat /etc/origin/master/master-config.yaml|grep PodPreset

On fresh installed v3.10 master host:
# cat /etc/origin/master/master-config.yaml |grep -A 5 PodPreset
    PodPreset:
      configuration:
        apiVersion: v1
        disable: true
        kind: DefaultAdmissionConfig
    openshift.io/ImagePolicy:

# grep -r "PodPreset"
roles/openshift_control_plane/tasks/upgrade.yml:    key: 'admissionConfig.pluginConfig.PodPreset'
roles/openshift_control_plane/templates/master.yaml.v1.j2:    PodPreset:

Checked that, installer has a task to remove admissionConfig.pluginConfig.PodPreset for upgrade(if this change is necessary?), but for fresh installation, PodPreset was set in master config templates.


Version-Release number of the following components:
ansible-2.4.4.0-1.el7ae.noarch
openshift-ansible-3.10.0-0.50.0.git.0.bd68ade.el7.noarch

How reproducible:
always

Steps to Reproduce:
1. Upgrade rpm installed ocp v3.9 to v3.10
2.
3.

Actual results:
admissionConfig.pluginConfig.PodPreset was different between upgrade ocp and fresh installed ocp.

Expected results:
master config after upgrade should be the same with fresh installation

Additional info:
Please attach logs from ansible-playbook with the -vvv flag