[fast-reboot] don't restore original image when no new image defined

ansible/roles/test/handlers/main.yml

@@ -60,3 +60,10 @@
 - name: Clean up apt
   become: true
   shell: apt-get autoremove -y; apt-get autoclean -y; apt-get clean -y
+
+- name: restore current image
+  shell: 'sonic_installer set_default {{ current_sonic_image.stdout }}'
+  become: true
+
+- name: reboot sonic
+  include: roles/test/tasks/common_tasks/reboot_sonic.yml

ansible/roles/test/tasks/fast-reboot.yml

@@ -124,6 +124,9 @@
         - name: Install a new SONiC image if requested
           shell: sonic_installer install -y {{ new_image_location }}
           become: true
+          notify:
+            - restore current image
+            - reboot sonic
 
       when: new_sonic_image is defined
 
@@ -199,12 +202,5 @@
         dest: '/tmp/'
         flat: yes
 
-    - block:
-      - name: Set previous image as default
-        shell: 'sonic_installer set_default {{ current_sonic_image.stdout }}'
-        become: true
-
-      - name: reboot
-        include: roles/test/tasks/common_tasks/reboot_sonic.yml
-
-      when: new_sonic_image is defined
+    - name: make sure all handlers run
+      meta: flush_handlers

ansible/test_sonic.yml

@@ -18,6 +18,7 @@
     - vars/docker_registry.yml
   roles:
     - { role: test, scope: 'sonic' }
+  force_handlers: true
 
 - hosts: [lldp_neighbors]
   gather_facts: no