Fix Remove revoked ceph apt-keys

when running the playbook it does appens that the apt_key task fails.
let's retry in case of failure to mimic the apt-key add that runs later.

Change-Id: Ie745496f515af1461bb8d03ba6b5c7cac5e71150

tasks/ceph_preinstall_apt.yml

@@ -19,6 +19,8 @@
     state: "absent"
   register: revoke_keys
   with_items: "{{ ceph_revoked_gpg_keys }}"
+  retries: 5
+  delay: 2
   when:
     - ceph_pkg_source == 'ceph'