Hardcode fedora nodeset to F29

In master we want to update fedora-latest to F30, the definition in this
branch is blocking this. We have two options:

- Remove the nodeset and follow master
- Rename the nodeset and keep it pinned for this branch

For previous stable branches we have chosen the first option, but I
think we should go for the second option now favoring stability. We can
always drop the nodeset lateron if it becomes broken.

Change-Id: I85ab8afa9a251a160d09b960a214ac579d3305df

.zuul.yaml

@@ -49,7 +49,7 @@
           - controller
 
 - nodeset:
-    name: devstack-single-node-fedora-latest
+    name: devstack-single-node-fedora-29
     nodes:
       - name: controller
         label: fedora-29
@@ -535,10 +535,10 @@
     voting: false
 
 - job:
-    name: devstack-platform-fedora-latest
+    name: devstack-platform-fedora-29
     parent: tempest-full-py3
     description: Fedora latest platform test
-    nodeset: devstack-single-node-fedora-latest
+    nodeset: devstack-single-node-fedora-29
     voting: false
 
 - job:
@@ -623,7 +623,7 @@
         - devstack-ipv6
         - devstack-platform-centos-7
         - devstack-platform-opensuse-15
-        - devstack-platform-fedora-latest
+        - devstack-platform-fedora-29
         - devstack-platform-xenial
         - devstack-multinode
         - devstack-multinode-xenial