Update deprecated stdout_callback setting

Author: stackhpc-ci

etc/kayobe/ansible.cfg

@@ -1,7 +1,7 @@
 [defaults]
 forks = 20
 # Use the YAML stdout callback plugin.
-stdout_callback = yaml
+callback_result_format = yaml
 # Use the stdout_callback when running ad-hoc commands.
 bin_ansible_callbacks = True
 # Disable fact variable injection to improve performance.