Backup ethercalc to hostname specific location

Previously we assumed ethercalc01 was the backup destination but we've
recently migrated to a new ethercalc02 running on Xenial. Update the bup
puppetry to use the hostname as the backup target on the remote server.

Change-Id: Ie3854d9cf0f154bcb15aa1e4655a764caa3c8506

modules/openstack_project/manifests/ethercalc.pp

@@ -28,7 +28,7 @@ class openstack_project::ethercalc (
   # is required like with mysql.
   include bup
   bup::site { 'ord.rax':
-    backup_user   => 'bup-ethercalc01',
+    backup_user   => "bup-$::hostname",
     backup_server => 'backup01.ord.rax.ci.openstack.org',
   }
 }