[lag_id] Add lagid to free_list when LC absent for 30 minutes (#542)

When LC is absent for 30 minutes, the database cleanup kicks in. When LagId is released, it needs to be appended to the SYSTEM_LAG_IDS_FREE_LIST

This PR works with the following 2 PRs:
sonic-net/sonic-swss#3303
sonic-net/sonic-buildimage#20369

Signed-off-by: mlok <marty.lok@nokia.com>

sonic-chassisd/scripts/chassisd

@@ -515,6 +515,7 @@ class ModuleUpdater(logger.Logger):
                 local lagid = redis.call('HGET', 'SYSTEM_LAG_ID_TABLE', lagname)\n\
                 redis.call('SREM', 'SYSTEM_LAG_ID_SET', lagid)\n\
                 redis.call('HDEL', 'SYSTEM_LAG_ID_TABLE', lagname)\n\
+                redis.call('rpush', 'SYSTEM_LAG_IDS_FREE_LIST', lagid)\n\
             end\n\
         end\n\
         return"