ceph-mon: always call ceph-create-keys

ceph-mon: always call ceph-create-keys

After the jewel release the mon startup does not generate keys, but it's
still harmless to call ceph-create-keys with jewel because this task has
a 'creates' argument that will cause it not to run if the keys already
exist.

Removing this when condition also allows the downstream CI tests to
install kraken or luminous without resetting ceph_stable_release, which does not
pertain to rhcs.

Signed-off-by: Andrew Schoen <aschoen@redhat.com>