Add system test lingering CLOSE_WAIT TCP sockets

Add system test lingering CLOSE_WAIT TCP sockets

Add a test case to check for lingering TCP sockets stuck in the
CLOSE_WAIT state. This can happen if a client sends some garbage after
its first query.

The system test runs the reproducer script and then sends another TCP
query to the resolver. The resolver is configured to allow one TCP
client only. If BIND has its TCP socket stuck in CLOSE_WAIT, it does
not have the resources available to answer the second query.

Note: A better test would be to check if the named daemon does not
have a TCP socket stuck in CLOSE_WAIT for example with netstat. When
running this test locally you can examine named with netstat manually.
But since netstat is platform specific it is not a good candidate to do
this as a system test.

If you, if you could return, don't let it burn.
Do you have to let it linger?
- Cranberries