tests/vm: add shutdown timeout in basevm.py

We are adding the shutdown timeout to solve an issue
we now see where the aarch64 VMs timeout on shutdown
under TCG.

There is a new 3 second timeout in machine.py,
which we override in basevm.py when shutting down.

Signed-off-by: Robert Foley <robert.foley@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20200717203041.9867-4-robert.foley@linaro.org>
Message-Id: <20200724064509.331-17-alex.bennee@linaro.org>
1 file changed