add juju availability zone to ceph osd location when present

The approach here is to use the availability zone as an imaginary rack.
All hosts that are in the same AZ will be in the same imaginary rack.
From Ceph's perspective this doesn't matter as it's just a bucket after all.
This will give users the ability to further customize their ceph deployment.

Change-Id: Ie25ac1b001db558d6a40fe3eaca014e8f4174241

templates/ceph.conf

@@ -29,6 +29,10 @@ public addr = {{ public_addr }}
 cluster addr = {{ cluster_addr }}
 {%- endif %}
 
+{% if crush_location %}
+osd crush location = {{crush_location}}
+{% endif %}
+
 
 [mon]
 keyring = /var/lib/ceph/mon/$cluster-$id/keyring