Pull RDO Trunk repos when CentOS Stream official RPM not available

The RDO project releases centos-release-openstack-* RPM a couple of
weeks after the OpenStack upstream project cut master branch.
In order to fill the gap in the meantime, we have to pull the repos
from RDO Trunk.

Change-Id: If95a687f2d7579779129eeb689cfa46b92450dc5
diff --git a/stack.sh b/stack.sh
index dcfd398..bfa0573 100755
--- a/stack.sh
+++ b/stack.sh
@@ -308,8 +308,11 @@
             # adding delorean-deps repo to provide current master rpms
             sudo wget https://trunk.rdoproject.org/centos9-master/delorean-deps.repo -O /etc/yum.repos.d/delorean-deps.repo
         else
-            # For stable/unmaintained branches use corresponding release rpm
-            sudo dnf -y install centos-release-openstack-${rdo_release}
+            if sudo dnf provides centos-release-openstack-${rdo_release} >/dev/null 2>&1; then
+                sudo dnf -y install centos-release-openstack-${rdo_release}
+            else
+                sudo wget https://trunk.rdoproject.org/centos9-${rdo_release}/delorean-deps.repo -O /etc/yum.repos.d/delorean-deps.repo
+            fi
         fi
     fi
     sudo dnf -y update