Switch to fedora-latest for nodeset name

To help avoid the amount zuul.yaml chrun when we bring a new version
of fedora online, switch to using fedora-latest. As of writing,
fedora-28 is the latest release which we update our testing for.

Also add fedora-28 support to stash.sh and remove fedora-25 /
fedora-26 as they are EOL.

Change-Id: I3d716554e8f270f4434cc9cac3408f8e890e0665
Depends-On: https://review.openstack.org/565758/
Signed-off-by: Paul Belanger <pabelanger@redhat.com>

.zuul.yaml

@@ -48,6 +48,16 @@
         nodes:
           - controller
 
+- nodeset:
+    name: devstack-single-node-fedora-latest
+    nodes:
+      - name: controller
+        label: fedora-28
+    groups:
+      - name: tempest
+        nodes:
+          - controller
+
 - nodeset:
     name: openstack-two-node
     nodes:
@@ -406,10 +416,10 @@
     voting: false
 
 - job:
-    name: devstack-platform-fedora-27
+    name: devstack-platform-fedora-latest
     parent: tempest-full
-    description: Fedora 27 platform test
-    nodeset: devstack-single-node-fedora-27
+    description: Fedora latest platform test
+    nodeset: devstack-single-node-fedora-latest
     voting: false
 
 - job:
@@ -482,7 +492,7 @@
         - devstack-platform-centos-7
         - devstack-platform-opensuse-423
         - devstack-platform-opensuse-tumbleweed
-        - devstack-platform-fedora-27
+        - devstack-platform-fedora-latest
         - devstack-multinode
         - devstack-unit-tests
     gate:

stack.sh

@@ -221,7 +221,7 @@ write_devstack_version
 
 # Warn users who aren't on an explicitly supported distro, but allow them to
 # override check and attempt installation with ``FORCE=yes ./stack``
-if [[ ! ${DISTRO} =~ (xenial|artful|bionic|stretch|jessie|f25|f26|f27|opensuse-42.3|opensuse-tumbleweed|rhel7) ]]; then
+if [[ ! ${DISTRO} =~ (xenial|artful|bionic|stretch|jessie|f27|f28|opensuse-42.3|opensuse-tumbleweed|rhel7) ]]; then
     echo "WARNING: this script has not been tested on $DISTRO"
     if [[ "$FORCE" != "yes" ]]; then
         die $LINENO "If you wish to run this script anyway run with FORCE=yes"