Manually set openstack_release to master

With the Kayobe 2025.1 release [1], openstack_release is no longer
"master" by default

[1] https://review.opendev.org/c/openstack/kayobe/+/949499

(cherry picked from commit d387213)

Author: seunghun1ee

etc/kayobe/openstack.yml

@@ -2,14 +2,16 @@
 ###############################################################################
 # OpenStack release configuration.
 
-# Name of the current OpenStack release. Default is "master".
-#openstack_release:
+# Name of the current OpenStack release. Default is "2025.1".
+openstack_release: master
 
 # Codename of the current OpenStack release.
 # NOTE(upgrade): Update to current release codename.
 openstack_release_codename: "epoxy"
 
-# Name of the current OpenStack branch. Default is "master".
+# Name of the current OpenStack branch. Default is "master" if
+# openstack_release is "master".
+# Otherwise, the default is "stable/{{ openstack_release }}".
 #openstack_branch:
 
 ###############################################################################