we already drop the lock between sending and receiving the rpc packets. now making it so that receive doesn't block for too long (ie 100ms) before unlocking the socket. this is needed for the callback. original rpc is sent and it triggers a callback from the server. we fork another thread to handle it, ie it needs to send a deleg_return rpc. if original rpc gets control and blocks on trying to receive its reply, it'll timeout and original rpc will return an error. instead we need to not block for long and allow the deleg_return to go thru so that the server can reply successfully to the original rpc.
we were checking for error result of send_null but not setting
status, then going to "out_unlock" and since status is NO_ERROR
trying to send bind_conn_to_session
