mds: rename mds_socket fact

Rename this fact to keep consistency with handlers in `ceph-defaults`.

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

roles/ceph-mds/tasks/docker/enable_multimds.yml

@@ -1,10 +1,10 @@
 ---
 - name: wait for mds socket to exist
   command: "{{ docker_exec_cmd }} stat /var/run/ceph/{{ cluster }}-mds.{{ ansible_hostname }}.asok"
-  register: mds_socket
+  register: multi_mds_socket
   retries: 5
   delay: 15
-  until: mds_socket.rc == 0
+  until: multi_mds_socket.rc == 0
 
 - name: enable multimds if requested when mon is containerized
   command: "{{ docker_exec_cmd }} ceph --cluster {{ cluster }} fs set {{ cephfs }} allow_multimds true --yes-i-really-mean-it"