Document additional cephadm role variables

Author: priteau

etc/kayobe/cephadm.yml

@@ -41,9 +41,16 @@ cephadm_cluster_network: "{{ storage_mgmt_net_name | net_cidr }}"
 # Whether to enable firewalld for Ceph storage hosts.
 #cephadm_enable_firewalld:
 
+# List of /dev/device paths to use, e.g. for multipath devices that can't be
+# used with an OSD spec.
+#cephadm_osd_devices:
+
 # Ceph OSD specification.
 #cephadm_osd_spec:
 
+# Additional arguments to pass to `cephadm bootstrap`.
+#cephadm_bootstrap_additional_parameters:
+
 ###############################################################################
 # Ceph post-deployment configuration.