tests/vm: Pass the jobs parallelism setting to 'make check'

Our test suite works for parallel execution too, and this can
noticeably speed up a test run; pass the 'jobs' setting to
it as well as to the build proper.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <20180803085230.30574-3-peter.maydell@linaro.org>
Signed-off-by: Fam Zheng <famz@redhat.com>
4 files changed