upgrade: skip luminous tasks for jewel minor update

These tasks are needed only when upgrading to luminous.
They are not needed in Jewel minor upgrade and by the way, they fail because
`ceph versions` command doesn't exist.

Signed-off-by: Guillaume Abrioux <gabrioux@redhat.com>

infrastructure-playbooks/rolling_update.yml

@@ -363,11 +363,15 @@
       command: "{{ docker_exec_cmd_update_osd|default('') }} ceph --cluster {{ cluster }} versions"
       register: ceph_versions
       delegate_to: "{{ groups[mon_group_name][0] }}"
+      when:
+        - not jewel_minor_update
 
     - name: set_fact ceph_versions_osd
       set_fact:
         ceph_versions_osd: "{{ (ceph_versions.stdout|from_json).osd }}"
       delegate_to: "{{ groups[mon_group_name][0] }}"
+      when:
+        - not jewel_minor_update
 
     # length == 1 means there is a single osds versions entry
     # thus all the osds are running the same version
@@ -375,8 +379,9 @@
       command: "{{ docker_exec_cmd_update_osd|default('') }} ceph --cluster {{ cluster }} osd require-osd-release luminous"
       delegate_to: "{{ groups[mon_group_name][0] }}"
       when:
-        - (ceph_versions.stdout|from_json).osd | length == 1
+        - (ceph_versions.get('stdout', '{}')|from_json).get('osd', {}) | length == 1
         - ceph_versions_osd | string | search("ceph version 12")
+        - not jewel_minor_update
 
 
 - name: upgrade ceph mdss cluster