test/py: Run simple dm commands without checking

Just to make sure that dm commands can operate.
This was the problem on Microblaze in past without fixing manual
relocation.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@amd.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Link: https://lore.kernel.org/r/e6c4b8b44445c16cee84436627642ccc9886f507.1657191580.git.michal.simek@amd.com