Remove the pre-update group and add a post-upgrade group

The post-upgrade group will be invoked from
I32330a05fa142fc92d73f68103429c4c2c1816ab

Change-Id: I31075498a9d395603ed5e40d65ea3db6d89adc6a

validations/openstack-endpoints.yaml

@@ -10,7 +10,7 @@
       groups:
       - post-deployment
       - pre-upgrade
-      - pre-update
+      - post-upgrade
   tasks:
   # Check connectivity to horizon
   - name: Check Horizon

validations/stack-health.yaml

@@ -8,6 +8,7 @@
         an upgrade.
       groups:
         - pre-upgrade
+        - post-upgrade
   tasks:
   - name: Check stack resource statuses
     assert:

validations/undercloud-service-status.yaml

@@ -6,7 +6,7 @@
       description: >
         Check undercloud status before running a stack update - especially minor update and major upgrade.
       groups:
-        - pre-update
+        - post-upgrade
         - pre-upgrade
   tasks:
   - name: Check Services are running