Do not hardcode image name and properly delete mock images in CI tests

Change-Id: I2962dd1d1c27989cbd135b051cfb3e9f8c9e3823

ci/roles/image/tasks/main.yml

@@ -318,6 +318,15 @@
          name: ansible_project
          domain: default
 
+    - name: Delete mock kernel and ramdisk images
+      openstack.cloud.image:
+         cloud: "{{ cloud }}"
+         state: absent
+         name: "{{ item }}"
+      loop:
+        - cirros-vmlinuz
+        - cirros-initrd
+
     - name: Delete test image file
       file:
          name: "{{ tmp_file.path }}"