validate: fail in check_devices at the right task

see https://bugzilla.redhat.com/show_bug.cgi?id=1648168#c17 for details.

Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1648168#c17

Signed-off-by: Guillaume Abrioux <gabrioux@redhat.com>
(cherry picked from commit 771648304d)

roles/ceph-validate/tasks/check_devices.yml

@@ -1,14 +1,17 @@
 ---
-- name: validate devices is actually a device
-  parted:
-    device: "{{ item }}"
-    unit: MiB
-  register: devices_parted
-  with_items: "{{ devices }}"
+- name: devices validation
+  when: devices is defined
+  block:
+    - name: get devices information
+      parted:
+        device: "{{ item }}"
+        unit: MiB
+      register: devices_parted
+      failed_when: False
+      with_items: "{{ devices }}"
 
-- name: fail if one of the devices is not a device
-  fail:
-    msg: "{{ item }} is not a block special file!"
-  when:
-    - item.failed
-  with_items: "{{ devices_parted.results }}"
+    - name: fail if one of the devices is not a device
+      fail:
+        msg: "{{ item }} is not a block special file!"
+      when: item.rc is defined
+      with_items: "{{ devices_parted.results }}"