Conditionally run appropriate db_sync commands

Take advantage of the return code given by keystone_manage db_sync's
'check' option to conditionally run the appropriate database migration
commands.

0 - currently up to date
1 - error requiring operator intervention
2 - expand required
3 - migrate required
4 - contract required

Related-Bug: 1642212
Change-Id: I129590ff6ac4e45bfd9b3ea21ad6615f66d37d31

tasks/keystone_db_setup.yml

@@ -27,16 +27,28 @@
     - "{{ keystone_wsgi_program_names }}"
     - "{{ keystone_system_service_name }}"
 
+- name: Check current state of Keystone DB
+  command: "{{ keystone_bin }}/keystone-manage db_sync --check"
+  register: keystone_db_sync_check
+  failed_when: keystone_db_sync_check.rc == 1
+  changed_when: "{{ keystone_db_sync_check.rc not in [2, 3, 4] }}"
+
 - name: Perform a Keystone DB sync expand
   command: "{{ keystone_bin }}/keystone-manage db_sync --expand"
-  changed_when: true
   become: yes
   become_user: "{{ keystone_system_user_name }}"
+  when: keystone_db_sync_check.rc == 2
 
 - name: Perform a Keystone DB sync migrate
   command: "{{ keystone_bin }}/keystone-manage db_sync --migrate"
-  changed_when: true
   become: yes
   become_user: "{{ keystone_system_user_name }}"
+  when: "{{ keystone_db_sync_check.rc in [2, 3] }}"
+  notify:
+    - Perform a Keystone DB sync contract
+
+- name: Check if Keystone DB sync contract is required
+  command: "true"
+  changed_when: keystone_db_sync_check.rc == 4
   notify:
     - Perform a Keystone DB sync contract