Adjust ordering for nova_db_setup

Running an api_db sync on an existing cluster without cells, for example
in an N->O upgrade requires the cells to have been setup.

Changing the ordering to setup the cells first before running the api_db
sync will resolve this.

However, in a greenfield deploy we require the api_db sync to happen
before we can create a cell. We should test to see if the api_db version
is 0 (it hasn't been setup yet) and then run the api_db sync if it
hasn't, otherwise skip to create the cell.

Closes-Bug: #1667127
Change-Id: If3fff46dd581294ef44cad0a1626b68229bca060

tasks/nova_db_setup.yml

@@ -13,11 +13,24 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+- name: Get the api_db version
+  command: "{{ nova_bin }}/nova-manage api_db version"
+  become: yes
+  become_user: "{{ nova_system_user_name }}"
+  register: nova_api_db_version
+  changed_when: false
+  tags:
+    - nova-db-setup
+    - nova-setup
+    - nova-command-bin
+
 - name: Perform a Nova API DB sync
   command: "{{ nova_bin }}/nova-manage --config-file /etc/nova/nova.conf api_db sync"
   become: yes
   become_user: "{{ nova_system_user_name }}"
   changed_when: false
+  when:
+    - nova_api_db_version.stdout == "0"
   tags:
     - nova-db-setup
     - nova-setup
@@ -45,6 +58,16 @@
     - nova-setup
     - nova-command-bin
 
+- name: Perform a Nova API DB sync
+  command: "{{ nova_bin }}/nova-manage --config-file /etc/nova/nova.conf api_db sync"
+  become: yes
+  become_user: "{{ nova_system_user_name }}"
+  changed_when: false
+  tags:
+    - nova-db-setup
+    - nova-setup
+    - nova-command-bin
+
 - name: Perform a Nova DB sync
   command: "{{ nova_bin }}/nova-manage --config-file /etc/nova/nova.conf db sync"
   become: yes