Install metrics-server pre-upgrade, if metrics

This installs metrics-server pre-upgrade, so that we don't break
existing HPAs.  In both the case of fresh installation and upgrade, we
deploy metrics-server if the user has configured metrics to be deployed,
so that we don't break existing installations.  The user can still
manually set `openshift_metrics_server_install=False` to disable this
behavior.

inventory/hosts.example

@@ -549,8 +549,9 @@ debug_level=2
 #openshift_metrics_install_metrics=true
 #
 # metrics-server deployment
-# By default, metrics-server is not automatically deployed.  Deploying metrics-server
-# is necessary to use the HorizontalPodAutoscaler.  Set this to enable it.
+# By default, metrics-server is not automatically deployed, unless metrics is also
+# deployed.  Deploying metrics-server is necessary to use the HorizontalPodAutoscaler.
+# Set this to enable it.
 #openshift_metrics_server_install=true
 #
 # Storage Options

playbooks/common/openshift-cluster/upgrades/v3_11/upgrade_control_plane.yml

@@ -66,6 +66,14 @@
 # TODO: need to verify settings about the bootstrap configs
 # 1. Does network policy match the master config
 
+- name: Ensure metrics-server is installed before upgrading the controller-manager
+  hosts: oo_first_master
+  roles:
+  - role: metrics_server
+    # a default is set on the actual variable in the role, so no fancy logic is needed here
+    when: openshift_metrics_server_install | default(true) | bool
+
+
 - name: Configure components that must be available prior to upgrade
   hosts: oo_first_master
   pre_tasks: