Failure to detect ``local_gb`` fails the Redfish inspection.
But ideally it shouldn't fail, for instance the node can be a
disk-less node.
Allow Redfish inspect operation now to ignore missing ``local_gb``
property and set it to 0 in such cases.
Change-Id: I96fa83b81372333e626cca0e64fefcd0aeabe031
Story: 2004622
Task: 28542
b8e720e51f