[fix:connection/tasks] Ignore current task instance when checking active tasks - #1204

The _is_update_in_progress function was incorrectly detecting the current
Celery task as another running task, causing update_config to exit early.

This fix excludes the current task by comparing task IDs, ensuring only
other instances for the same device are considered. Added tests to cover
same worker (should not skip) and different worker (should skip) scenarios.

Additionally, added INFO-level logging to convey when a task is skipped
because another task is in progress.

Author: piyushdev04

openwisp_controller/connection/tasks.py

@@ -53,6 +53,7 @@ def update_config(device_id):
         logger.warning(f'update_config("{device_id}") failed: {e}')
         return
     if _is_update_in_progress(device_id):
+        logger.info(f"Skipping update_config for device {device_id} as another task is in progress.")
         return
     try:
         device_conn = DeviceConnection.get_working_connection(device)