Fedora: Mark Fedora 31 as supported and use within fedora-latest

Change-Id: I06235eb5bf722e6f3ab05da577fa0f00638c87b1
diff --git a/.zuul.yaml b/.zuul.yaml
index cc97b89..48c2d0d 100644
--- a/.zuul.yaml
+++ b/.zuul.yaml
@@ -52,7 +52,7 @@
     name: devstack-single-node-fedora-latest
     nodes:
       - name: controller
-        label: fedora-30
+        label: fedora-31
     groups:
       - name: tempest
         nodes:
diff --git a/stack.sh b/stack.sh
index 9879bd4..4e1134b 100755
--- a/stack.sh
+++ b/stack.sh
@@ -221,7 +221,7 @@
 
 # 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} =~ (bionic|stretch|jessie|f30|opensuse-15.0|opensuse-15.1|opensuse-tumbleweed|rhel7) ]]; then
+if [[ ! ${DISTRO} =~ (bionic|stretch|jessie|f30|f31|opensuse-15.0|opensuse-15.1|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"