After r366857, TCP sessions are hanging on shutdown. This occurs when the shutdown script shuts down the network interfaces before init kills off remaining processes with open TCP connections. (For example, incoming SSH sessions are not killed off until after init is finished running the shutdown scripts.)
This change will kill off all TCP connections only when the script is shutting down all network interfaces. When a user is shutting down only some network interfaces, it is non-trivial to determine which TCP connections may be impacted.