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: Ibc6f84428699a0a54c0f24d54b1390af6a041f9f
Closes-Bug: #1633438
Signed-off-by: Kevin Carter <kevin.carter@rackspace.com>

tasks/nova_compute_powervm_install.yml

@@ -21,7 +21,6 @@
   until: add_nv_keys|success
   retries: 5
   delay: 2
-  ignore_errors: True
   with_items: "{{ novalink_gpg_keys }}"
   tags:
     - novalink-apt-keys

tasks/nova_install.yml

@@ -105,7 +105,7 @@
     url: "{{ nova_venv_download_url }}"
     dest: "/var/cache/{{ nova_venv_download_url | basename }}"
     force: yes
-  ignore_errors: true
+  failed_when: false
   register: get_venv
   when:
     - not nova_developer_mode | bool