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: I5ceece61312e2bf39d7489261bca247f353d6d74
Closes-Bug: #1633438
Signed-off-by: Kevin Carter <kevin.carter@rackspace.com>

tasks/keystone_apache.yml

@@ -94,7 +94,7 @@
   apache2_module:
     name: shib2
     state: "{{ ( keystone_sp != {} ) | ternary('present', 'absent') }}"
-  ignore_errors: yes
+  failed_when: false
   when:
     - ansible_pkg_mgr == 'apt'
   notify:

tasks/keystone_install.yml

@@ -101,7 +101,7 @@
     url: "{{ keystone_venv_download_url }}"
     dest: "/var/cache/{{ keystone_venv_download_url | basename }}"
     force: yes
-  ignore_errors: true
+  failed_when: false
   register: get_venv
   when:
     - not keystone_developer_mode | bool