Correct log warning for unknown lvalue

The default systemd service template was using the PrivateUsers
directive by default which was only implemented in systemd version 232.
Because we're running on older versions of systemd in a lot of cases the
this option was creating a log of journal spam. To correct the issue the
version of systemd is now detected and this default option will only be
used when the version of systemd is greater than or equal to version
232.

Change-Id: Ief1a2e155892ab7df821fbf049787e705da91b40
Closes-Bug: #1776818
Signed-off-by: Kevin Carter <kevin.carter@rackspace.com>

tasks/main.yml

@@ -13,6 +13,21 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+- name: Pull systemd version
+  command: "systemctl --version"
+  changed_when: false
+  register: get_systemd_version
+  tags:
+    # Avoid ANSIBLE0006 lint issue: systemctl used in place of systemd module
+    - skip_ansible_lint
+    - always
+
+- name: Set systemd version
+  set_fact:
+    systemd_version: "{{ get_systemd_version.stdout_lines[0].split()[-1] }}"
+  tags:
+    - always
+
 - name: Create TEMP run dir
   file:
     path: "/var/run/{{ item.service_name | replace(' ', '_') }}"

templates/systemd-service.j2

@@ -73,7 +73,13 @@ TasksAccounting={{ systemd_TasksAccounting }}
 PrivateTmp={{ systemd_PrivateTmp }}
 PrivateDevices={{ systemd_PrivateDevices }}
 PrivateNetwork={{ systemd_PrivateNetwork }}
+{# NOTE(cloudnull): Limit the use of PrivateUsers
+   The systemd directive "PrivateUsers" was implemented in systemd version 232.
+   To correct a lot of spam messages in the journal the default directive is
+   limited when to systemd version greater than or equal to 232 #}
+{%     if (systemd_version | int) >= 232 %}
 PrivateUsers={{ systemd_PrivateUsers }}
+{%     endif %}
 {%   endif %}
 {% endif %}