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: Ide6ae6a5ea5d2279c42003f379b3a3460e62a525
Closes-Bug: #1633438
Signed-off-by: Kevin Carter <kevin.carter@rackspace.com>
(cherry picked from commit 2ef2b9e735)

tasks/ceilometer_install.yml

@@ -85,7 +85,7 @@
     url: "{{ ceilometer_venv_download_url }}"
     dest: "/var/cache/{{ ceilometer_venv_download_url | basename }}"
     force: yes
-  ignore_errors: true
+  failed_when: false
   register: get_venv
   when:
     - not ceilometer_developer_mode | bool

tests/test-install-mongodb.yml

@@ -68,7 +68,7 @@
         password: "{{ ceilometer_container_db_password }}"
         roles: 'root'
         state: present
-      ignore_errors: True
+      failed_when: false
 
     - name: Add ceilometer database user
       mongodb_user: