tests/vm: add 1GB extra memory per core

tests/vm: add 1GB extra memory per core

If you try to run a 16 or 32 threaded test, you're going to run out of
memory very quickly with qom-test and a few others. Bump the memory
limit to try to scale with larger-core machines.

Granted, this means that a 16 core processor is going to ask for 16GB,
but you *probably* meet that requirement if you have such a machine.

512MB per core didn't seem to be enough to avoid ENOMEM and SIGABRTs in
the test cases in practice on a six core machine; so I bumped it up to
1GB which seemed to help.

Add this magic in early to the configuration process so that the
config file, if provided, can still override it.

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Acked-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20220708153503.18864-9-jsnow@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>