Merge pull request #513 from tamsky/ansible/improve-raspbian-checks

contrib/ansible/roles/raspbian/tasks/main.yml

 ---
 
+- name: Test for Raspbian
+  stat:
+    path: /boot/cmdline.txt
+  register: cmdline
+
 - name: Activating cgroup on Raspbian
   lineinfile:
     path: /boot/cmdline.txt
     regexp: '^(.*rootwait)$'
     line: '\1 cgroup_enable=cpuset cgroup_memory=1 cgroup_enable=memory'
     backrefs: true
-  when: ( ansible_facts.architecture is search "arm" )
+  when: ( cmdline.stat.path is defined )
+          and
+        ( ansible_facts.architecture is search("arm") )
+  register: boot_cmdline
 
 - name: Rebooting on Raspbian 
   shell: reboot now
   ignore_errors: true
-  when: ( ansible_facts.architecture is search "arm" )
+  when: ( boot_cmdline | changed )
+          and
+        ( ansible_facts.architecture is search("arm") )