client: keyrings aren't created when single client node

client: keyrings aren't created when single client node

combining `run_once: true` with `inventory_hostname ==
groups.get(client_group_name) | first` might cause bug when the only
node being run is not the first in the group.

In a deployment with a single client node it might cause issue because
sometimes keyring won't be created since the task could be definitively
skipped.

Closes: https://bugzilla.redhat.com/show_bug.cgi?id=1588093
Signed-off-by: Guillaume Abrioux <gabrioux@redhat.com>