Improve condition checking about docker registry config

Avoids use of ignore_errors on a task that is only reading the status.

We only use the result code (rc) of the check so the task iself
should not fail regardless if the registry was managed or not.

Improves output of ansible console and confusing false errors.

Change-Id: I0be5f333a7ac6705279820a1a34667b4ec32f760

tasks/docker.yml

@@ -8,10 +8,13 @@
   command: grep -Fq "# Configured by Ansible container registry role" /etc/sysconfig/docker
   register: is_configured
   check_mode: false
-  ignore_errors: true
+  failed_when: false
   changed_when: false
 
-- block:
+- name: configure docker registry block
+  when: not container_registry_skip_reconfiguration or is_configured.rc != 0
+  become: true
+  block:
     # NOTE(aschultz): LP#1750194 - need to set ip_forward before docker starts
     # so lets set it before we install the package if we're managing it.
     - name: enable net.ipv4.ip_forward
@@ -150,6 +153,3 @@
         line: "# Configured by Ansible container registry role"
         insertafter: "^# /etc/sysconfig/docker$"
         create: yes
-
-  become: true
-  when: not container_registry_skip_reconfiguration or is_configured.rc != 0