libnvdimm, testing: update the default smart ctrl_temperature

The default value for smart ctrl_temperature was the same as the
threshold for ctrl_temperature. As a result, any arbitrary smart
injection to the nfit_test dimm could cause this alarm to trigger
and cause an acpi notification. Drop the default value to below the
threshold, so that unrelated injections don't trigger notifications.

Cc: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>