Use dict args for ceph_config slurp

Very minor style change, slurp was added with string args (slurp src=)
This patch converts that to using dictionary style args.

Change-Id: I6290d7c993aa561e1b1d2864ebc2884be41f9330
Implements: blueprint ceph-block-devices

playbooks/roles/ceph_client/tasks/ceph_config.yml

@@ -24,7 +24,8 @@
     - ceph-config-create-dir
 
 - name: Get ceph.conf and store contents when ceph_conf_file is not defined
-  slurp: src=/etc/ceph/ceph.conf
+  slurp:
+    src: /etc/ceph/ceph.conf
   register: ceph_conf_content_mon
   delegate_to: '{{ ceph_mon_host }}'
   changed_when: false