We were having a problem where the system-suspend test was passing,
but then the next test - gem-execbuf-stress - was failing because of
bugs caused by the suspend subtest. So add a single test that emulates
the same problem, and another test that just sets a mode after resume.
This way, we should be reproducing the problem even if you don't run
the tests in the order they are defined.

Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>