Use block/rescue for error handling

Instead of allowing the first task to fail, then
using the fallback - use block/rescue to achieve
the same, but totally skip the second task if the
first succeeds.

Change-Id: Icb4ce1901a5a4c2b870b308f7cd6444b304a022a

tasks/ceph_preinstall_apt.yml

@@ -23,44 +23,45 @@
     - ceph_pkg_source == 'ceph'
 
 - name: Add ceph apt-keys
-  apt_key:
-    id: "{{ item.hash_id }}"
-    keyserver: "{{ item.keyserver | default(omit) }}"
-    data: "{{ item.data | default(omit) }}"
-    url: "{{ item.url | default(omit) }}"
-    state: "present"
-  register: add_keys
-  until: add_keys|success
-  failed_when: false
-  retries: 5
-  delay: 2
-  with_items: "{{ ceph_gpg_keys }}"
-  when:
-    - ceph_pkg_source == 'ceph'
+  block:
+    - name: Add keys (primary keyserver)
+      apt_key:
+        id: "{{ item.hash_id }}"
+        keyserver: "{{ item.keyserver | default(omit) }}"
+        data: "{{ item.data | default(omit) }}"
+        url: "{{ item.url | default(omit) }}"
+        state: "present"
+      register: add_keys
+      until: add_keys|success
+      retries: 5
+      delay: 2
+      with_items: "{{ ceph_gpg_keys }}"
+      when:
+        - ceph_pkg_source == 'ceph'
 
-- name: Add ceph apt-keys using fallback keyserver
-  apt_key:
-    id: "{{ item.hash_id }}"
-    keyserver: "{{ item.fallback_keyserver | default(omit) }}"
-    url: "{{ item.fallback_url | default(omit) }}"
-    state: "present"
-  register: add_keys_fallback
-  until: add_keys_fallback|success
-  retries: 5
-  delay: 2
-  with_items: "{{ ceph_gpg_keys }}"
-  when:
-    - ceph_pkg_source | lower == 'ceph'
-    - add_keys | failed
-    - item.fallback_keyserver is defined or item.fallback_url is defined
+  rescue:
+    - name: Add keys (fallback keyserver)
+      apt_key:
+        id: "{{ item.hash_id }}"
+        keyserver: "{{ item.fallback_keyserver | default(omit) }}"
+        url: "{{ item.fallback_url | default(omit) }}"
+        state: "present"
+      register: add_keys_fallback
+      until: add_keys_fallback|success
+      retries: 5
+      delay: 2
+      with_items: "{{ ceph_gpg_keys }}"
+      when:
+        - ceph_pkg_source == 'ceph'
+        - item.fallback_keyserver is defined or item.fallback_url is defined
 
 - name: add ubuntu cloud archive key package
   apt:
     pkg: ubuntu-cloud-keyring
     state: "{{ ceph_client_package_state }}"
   register: add_keys
   when:
-    - ceph_pkg_source | lower == 'uca'
+    - ceph_pkg_source == 'uca'
 
 - name: Add ceph repo(s)
   apt_repository: