fix(security): fix bug in negotiation_service::on_negotiation_request when rpc_session is closed

[levy5307]

1. Previously, if one rpc session is disconnected, we should remove the corresponding negotiation in negotiation_service.

In multi-thread environment, if thread A receive a negotiation message, and pass this message to negotiation_service::on_negotiation_request, which will find the correspoing negotiation to deal with this negotiation message.

And before this message is passed to negotiation_service::on_negotiation_reques, thread B receive a message which is illegal to process(for example: get operation), which will produce the rpc_session disconnected. In the meanwhile, the negotiation is removed.

So in negotiation_service::on_negotiation_request of thead A, the corresponding negotiation will be nullptr, this will produce a coredump.

Here is the process progress:

thread A:     -->receive nego msg--------------------------------------------------------------->get negotiation----->......---->

thread B: --------> receive get mesage-->close rpc_session-->remove negotiation----->......----->

Same situation with client_negotiation processing response.

2. The ownership of the negotiation instance is held by rpc_session, because I refactor it before. security is on the upper level of network now. So negotiation is better to have the ownership of rpc_session.

3. change the name from negotiaiton_service to negotiation_manager