Description of problem:

When installing the custom wildcard certificate for the router by following the documentation, the rolling deployment of the router is failing giving error failed to mount for metrics-server-certificate where metrics is not installed in the environment. 
The deploy_router.yml and redeploy-certificates.yml playbooks are completed without any failure.

- https://docs.openshift.com/container-platform/3.10/install_config/certificate_customization.html#configuring-custom-certificates-wildcard


Version-Release number of selected component (if applicable):
OCP 3.10 

How reproducible:
It was also observed in 3.10 and 3.11 clusters

Expected results:
In the OCP environment without metrics, the router deployment should be successful.

Additional information:

The errors from the events are as below:
1: "Failed mount" with the message "MountVolume.SetUp failed for volume "metrics-server-certificate" : secrets "router-metrics-tls" not found".
2: "Failed mount" with the message "Unable to mount volumes for pod "router-XX-XXX_default(XXX)": timeout expired waiting for volumes to attach or mount for pod "default"/"router-XX-XXX". list of unmounted volumes=[metrics-server-certificate]. list of unattached volumes=[metrics-server-certificate server-certificate router-token-XXX]"

After deletion of the secret and the two variables i.e. ROUTER_METRICS_TLS_CERT_FILE and ROUTER_METRICS_TLS_KEY_FILE, the wildcard certificate on out routes can be used.