cmd-coreos-prune: Only add policy-cleanup when needed

We are adding empty policy-cleanup key:value for the build even
when no pruning action in completed. Added changes to not do that
anymore.

Author: gursewak1997

src/cmd-coreos-prune

@@ -190,8 +190,10 @@ def main():
                                 else:
                                     print(f"No container tags to prune for build {build_id}.")
                     actions_completed.append(action)  # Append action to completed list
+        # Only add policy-cleanup for the build in builds.json if either of the action is completed
+        if actions_completed:
+            policy_cleanup = build.setdefault("policy-cleanup", {})
         # Update policy-cleanup for completed actions
-        policy_cleanup = build.setdefault("policy-cleanup", {})
         for action in actions_completed:
             if action == "images":
                 policy_cleanup["images-kept"] = images_to_keep