[BugFix] Fix request output loss during putting back to the api server

[s5u13b]

Found some request outputs are not written back to the api server. This is caused by server_infos of ignored_seq_groups are not added into the server_info_list.

1. Fix the request output loss through adding server_infos of ignored_seq_groups into server_info_list
2. Fix missing scheduler lock when changing waiting queue in add_request of llm_engine