Use fedora-30 as the fedora-latest image

With the open-iscsi rebase we should now be able to move the
fedora-latest job to fedora 30 ahead of the removal of support for 29.

Change-Id: Ia80f03f275e595d3b26b52b3478f303036d59438

Author: lyarwood

.zuul.yaml

@@ -52,7 +52,7 @@
     name: devstack-single-node-fedora-latest
     nodes:
       - name: controller
-        label: fedora-29
+        label: fedora-30
     groups:
       - name: tempest
         nodes: