Limit LXC hosts playbook to container hosts only

This will limit the lxc-hosts-setup playbook to run against only
the hosts which will receive LXC containers. This prevents LXC
package installation and cache preparation on hosts such as
compute_hosts which will not build any containers.

Change-Id: I002158d6539603ddb86d4b7ea1e4a16bb4ced81f

playbooks/lxc-hosts-setup.yml

@@ -14,7 +14,18 @@
 # limitations under the License.
 
 - name: Basic lxc host setup
-  hosts: "{{ lxc_host_group|default('hosts') }}"
+  hosts: >
+    {{ lxc_host_group |
+       default('
+         shared-infra_hosts
+         :os-infra_hosts
+         :repo-infra_hosts
+         :identity_hosts
+         :storage-infra_hosts
+         :log_hosts
+         :network_hosts
+       ')
+    }}
   gather_facts: "{{ gather_facts | default(True) }}"
   max_fail_percentage: 20
   user: root

releasenotes/notes/lxc-hosts-limit-9784050b888ea7c8.yaml

@@ -0,0 +1,7 @@
+---
+upgrade:
+  - LXC package installation and cache preparation will now occur by default
+    only on hosts which will actually implement containers.
+fixes:
+  - LXC package installation and cache preparation will now occur by default
+    only on hosts which will actually implement containers.