In some cases, BIND is not fast enough to fill the send buffer and
manages to answer all queries, contrary to what the test expects.
Repeat the check up to 3 times to limit this test instability.
It is better to use consistent file names to avoid issue with sorting
etc.
Using underscore in filenames as opposed to dash was chosen because it
seems more common in pytest/python to use underscore for filenames.
Also rename the bin/tests/system/timeouts/tests-tcp.py file to
bin/tests/system/timeouts/tests_tcp_timeouts.py to avoid pytest name
collision (there can't be two files named tests_tcp.py).