Add ability to change apt/yum package state

The current method of installing the distribution packages required is
set in the tasks and cannot be changed by a deployer.

Currently the apt task always installs the latest package. This results
in unexpected binary changes when a deployer may simply be trying to
execute a configuration change.

This patch adds the ability for a deployer to change the desired state
so that the results are predictable.

Change-Id: If2e9de4c86a9b9cc6cd19c44e5555c68b7dbf286

defaults/main.yml

@@ -13,6 +13,10 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+# Set the package install state for distribution packages
+# Options are 'present' and 'latest'
+lxc_hosts_package_state: "latest"
+
 # Mappings from Ansible reported architecture to distro release architecture
 lxc_architecture_mapping:
   x86_64: amd64

releasenotes/notes/package-state-c9c7e01e77b596d0.yaml

@@ -0,0 +1,14 @@
+---
+features:
+  - The lxc_hosts role now supports the ability to configure whether
+    apt/yum tasks install the latest available package, or just ensure
+    that the package is present. The default action is to ensure that
+    the latest package is present. The action taken may be changed to
+    only ensure that the package is present by setting
+    ``lxc_hosts_package_state`` to ``present``.
+upgrade:
+  - The lxc_hosts role always checks whether the latest package is
+    installed when executed. If a deployer wishes to change the check to
+    only validate the presence of the package, the option
+    ``lxc_hosts_package_state`` should be set to ``present``.
+

tasks/lxc_install_apt.yml

@@ -33,7 +33,7 @@
 - name: Install apt packages
   apt:
     pkg: "{{ item }}"
-    state: latest
+    state: "{{ lxc_hosts_package_state }}"
     default_release: "{{ lxc_default_release | default(omit) }}"
   register: install_packages
   until: install_packages|success