tools:sst-compare-redfish-os: Handle missing properties

Turns out there are some properties not exposed by the
intel-speed-select tool, so we need to handle missing values without
failing the test.

Tested: Ran sst-compare-redfish-os.py:
...
Junction Temperature:
  Redfish: 81
  Linux: 81
SSE Max Turbo Speed: MISSING VALUE
  Redfish: 3500
  Linux: None
TDP:
  Redfish: 250
  Linux: 250
...
Everything matched! :)

Signed-off-by: Jonathan Doman <jonathan.doman@intel.com>
Change-Id: Ia34ee13879801eb0c351508ccc7d906bf5e122e0
1 file changed