Remove 'ignore_errors: true' in favor of 'failed_when: false'

This change removes the use of 'ignore_errors: true' because it causes deployers
to see red output and a stacktrace, which traditionally means something is broken,
even when the failure is known to have a fall back option or be intentional. This
conversion will provide a generally cleaner interface.

It should be noted that the 'failed' filter will still function normally. Tasks
with the 'failed_when: false' option will still be marked as 'failed' in any
registered variable. This change simply makes the output look cleaner.

Change-Id: I2c1b39905720e8e6ecb51d88f36c9eb47329d328
Closes-Bug: #1633438
Signed-off-by: Kevin Carter <kevin.carter@rackspace.com>

tasks/galera_client_install_apt.yml

@@ -51,7 +51,7 @@
   until: add_keys|success
   retries: 5
   delay: 2
-  ignore_errors: true
+  failed_when: false
   tags:
     - galera-client-apt-keys
 

tasks/galera_client_install_yum.yml

@@ -48,7 +48,7 @@
     key: "{{ item.keyserver }}/{{ item.key_name }}"
   register: add_keys
   until: add_keys|success
-  ignore_errors: True
+  failed_when: false
   retries: 5
   delay: 2
   with_items: "{{ galera_client_gpg_keys }}"