nbd netlink refactoring (#1963)

nbd netlink refactoring

- fix context leak when nl_socket_modify_cb fails
- use clojure instead of a static method + custom context as a socket callback
- move TNetlinkDevice methods outside of the class definition to reduce nesting
- use nl_send_auto + nl_wait_for_ack instead of nl_send_sync to differentiate between send and recv errors
- remove "Device" suffixes from TNetlinkDevice methods