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: I6336a5821498412b1be3930daad5553342872875

metadata.json

@@ -79,5 +79,5 @@
     ],
     "source": "https://opendev.org/openstack/puppet-ironic.git",
     "summary": "Puppet module for OpenStack Ironic",
-    "version": "18.6.0"
+    "version": "18.7.0"
 }