Use yml extension for pytest tests

The pytest .yaml files have been rename to .yml to enable
build-galaxy-release to fix the prefix of the ansible-freeipa modules.

tests/pytests/dnszone/playbooks/dnszone_invalid_serial.yml

@@ -0,0 +1,11 @@
+---
+- name: Playbook to ensure, not able to add invalid(more than 4294967295) serial numbers.
+  hosts: ipaserver
+  become: true
+
+  tasks:
+  - name: Test adding a DNS zone with an invalid serial
+    ipadnszone:
+      ipaadmin_password: SomeADMINpassword
+      name: invalidserialzone.test
+      serial: 429496729599