tests/avocado: Replace assertEquals() for Python 3.12 compatibility

tests/avocado: Replace assertEquals() for Python 3.12 compatibility

assertEquals() has been removed in Python 3.12 and should be replaced by
assertEqual(). See: https://docs.python.org/3.12/whatsnew/3.12.html#id3

Message-ID: <20231114134326.287242-1-thuth@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Thomas Huth <thuth@redhat.com>
(cherry picked from commit 861f724d03e1748cda1c5b9ec8457a368590cbd5)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
(Mjt: adjust context in pc_cpu_hotplug_props.py & cpu_queries.py for before
 v8.1.0-1582-g684750ab4f "python/qemu: rename command() to cmd()")