Fix the prechecks role idempotent

the prechecks role should be idempotent and should changed nothing when
running.

TrivialFix

Change-Id: Ib5063d879e0f5f414d607bd9b6493a7499fc5652

ansible/roles/prechecks/tasks/package_checks.yml

@@ -2,10 +2,12 @@
 - name: Checking docker-py version
   command: python -c "import docker; print docker.__version__"
   register: result
+  changed_when: false
   failed_when: result | failed or
                result.stdout | version_compare(docker_py_version_min, '<')
 
 - name: Checking Ansible version
   local_action: command ansible --version
   register: result
+  changed_when: false
   failed_when: result.stdout | regex_replace('ansible (\\d+\\.\\d+\\.\\d+)', '\\1') | version_compare(ansible_version_max, '>=')

ansible/roles/prechecks/tasks/service_checks.yml

@@ -8,12 +8,14 @@
 - name: Checking Docker version
   command: docker version
   register: result
+  changed_when: false
   failed_when: result | failed
                or (result.stdout | from_yaml).Server.Version | regex_replace('(\\d+\\.\\d+\\.\\d+).*', '\\1') | version_compare(docker_version_min, '<')
 
 - name: Checking if 'MountFlags' in /lib/systemd/system/docker.service is set to 'shared'
   command: cat /lib/systemd/system/docker.service
   register: result
+  changed_when: false
   failed_when: result.stdout.find('MountFlags=shared') == -1
   when:
     - (inventory_hostname in groups['neutron-dhcp-agent']
@@ -25,6 +27,7 @@
 - name: Checking if '/run' mount flag is set to 'shared'
   command: awk '$5 == "/run" {print $7}' /proc/self/mountinfo
   register: result
+  changed_when: false
   failed_when: result.stdout.find('shared') == -1
   when:
     - (inventory_hostname in groups['neutron-dhcp-agent']