Prepare the final wallaby release

... to create a release with a few bug fixes and new features, which
were merged after the last wallaby release.

Change-Id: Ia102e317903b2dd9426d46be061a897b7577431f

metadata.json

@@ -79,5 +79,5 @@
     ],
     "source": "https://opendev.org/openstack/puppet-swift.git",
     "summary": "Puppet module for OpenStack Swift",
-    "version": "18.5.0"
+    "version": "18.6.0"
 }