ctdb-scripts: Compact server-end TCP connection killing output

ctdb-scripts: Compact server-end TCP connection killing output

When thousands of connections are being killed the logs are flooded
with information about connections that should be killed.  When some
connections are not killed then the number not killed is printed.
This is the wrong way around!  When debugging "fail-back" problems, it
is important to know details of connections that were *not* killed.
It is almost never important to know the full list of all connections
that were *supposed* to be killed.

Instead, print a summary showing how many connections of the total
were killed.  If any were not killed then print a list of remaining
connections.

Update unit tests: infrastructure for fake TCP connections, existing,
test cases, add new test cases.

Signed-off-by: Martin Schwenke <martin@meltin.net>
Reviewed-by: Amitay Isaacs <amitay@gmail.com>