Support openshift_upgrade_dry_run=true for pre-upgrade checks only.

inventory/byo/hosts.origin.example

@@ -99,6 +99,8 @@ openshift_release=v1.2
 # modify image streams to point at that registry by setting the following to true
 #openshift_examples_modify_imagestreams=true
 
+# Perform only pre-upgrade checks, and exit.
+# openshift_upgrade_dry_run=true
 
 # Origin copr repo
 #openshift_additional_repos=[{'id': 'openshift-origin-copr', 'name': 'OpenShift Origin COPR', 'baseurl': 'https://copr-be.cloud.fedoraproject.org/results/maxamillion/origin-next/epel-7-$basearch/', 'enabled': 1, 'gpgcheck': 1, 'gpgkey': 'https://copr-be.cloud.fedoraproject.org/results/maxamillion/origin-next/pubkey.gpg'}]

inventory/byo/hosts.ose.example

@@ -99,6 +99,9 @@ openshift_release=v3.2
 # modify image streams to point at that registry by setting the following to true
 #openshift_examples_modify_imagestreams=true
 
+# Perform only pre-upgrade checks, and exit.
+# openshift_upgrade_dry_run=true
+
 # Additional yum repos to install
 #openshift_additional_repos=[{'id': 'ose-devel', 'name': 'ose-devel', 'baseurl': 'http://example.com/puddle/build/AtomicOpenShift/3.1/latest/RH7-RHOSE-3.0/$basearch/os', 'enabled': 1, 'gpgcheck': 0}]
 

playbooks/common/openshift-cluster/upgrades/pre.yml

@@ -309,3 +309,10 @@
   - fail:
       msg: "Upgrade cannot continue. The following hosts did not complete etcd backup: {{ etcd_backup_failed | join(',') }}"
     when: etcd_backup_failed | length > 0
+
+- name: Exit upgrade if dry-run specified
+  hosts: oo_first_master
+  tasks:
+  - fail:
+      msg: "Pre-upgrade checks completed, exiting due to openshift_upgrade_dry_run variable."
+    when: openshift_upgrade_dry_run is defined and openshift_upgrade_dry_run | bool