roles: ceph-defaults: Delegate cluster information task to monitor node

roles: ceph-defaults: Delegate cluster information task to monitor node

Since commit f422efb1d6b56ce56a7d39a21736a471e4ed357 ("config: ensure
rgw section has the correct name") we observe the following failures in
new Ceph deployment with OpenStack-Ansible

fatal: [aio1_ceph-rgw_container-fc588f0a]: FAILED! => {"changed": false,
"cmd": "ceph --cluster ceph -s -f json", "msg": "[Errno 2] No such file
or directory"

This is because the task executes 'ceph' but at this point no package
installation has happened. Packages are normally installed in the
'ceph-common' role which runs after the 'ceph-defaults' one.

Since we are looking to obtain cluster information, the task should be
delegated to a monitor node similar to other tasks in that role

Signed-off-by: Markos Chandras <mchandras@suse.de>