tests/avocado: probe for multi-process support before running test

A recent attempt to let avocado run more tests on the CentOS stream
build failed because there was no gating on the multiprocess feature.
Like missing accelerators avocado should gracefully skip when the
feature is not enabled.

In this case we use the existence of the proxy device as a proxy for
multi-process support.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Cc: Elena Ufimtseva <elena.ufimtseva@oracle.com>
Cc: Jagannathan Raman <jag.raman@oracle.com>
Cc: John G Johnson <john.g.johnson@oracle.com>
Message-Id: <20230321111752.2681128-1-alex.bennee@linaro.org>
2 files changed