ci: fix various issues preventing complete runs

When creating a coe cluster, a flavor lookup occurs which
fails as nothing is specified. This adds a default flavor
which can be used to test cluster provisioning.

Various checks used a deprecated truthy check which no
longer works with Ansible 2.19

Inventory cache format change in Ansible 2.19

galaxy.yml required in tmp testing directory or version
checks fail for linters with Ansible 2.19

Change-Id: Iaf3f05d0841a541e4318821fe44ddd59f236b640

ci/roles/network/tasks/main.yml

@@ -11,7 +11,7 @@
 - name: Check output of creating network
   assert:
     that:
-      - infonet.network
+      - infonet.network is defined
       - item in infonet.network
   loop: "{{ expected_fields }}"