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).
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