Use check_mode instead of always_run

This patch changes the `always_run: yes` task option to
`check_mode: no` to avoid Ansible warnings.

tasks/main.yml

@@ -3,7 +3,7 @@
   shell: ls -1 /etc/ceph/*.keyring
   changed_when: false
   register: ceph_keys
-  always_run: true
+  check_mode: no
 
 - name: set keys permissions
   file: