Azure: Split sandbox and qemu test.py runs

Currently, most sandbox runs take a long time (due to running so many
tests) while QEMu based test.py runs are fairly short.  Split the
pipeline here so that we get more consistent average run times.

Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>