The iDRACCard attribute GroupID is empty for 15th Generation servers,
e.g., Dell EMC PowerEdge R750 and R650, which triggered the error
"attribute GroupID is not nullable".
A similar error message has been observed when processing the
iDRACCardInteger attributes LowerBound and UpperBound read
from a PowerEdge XE2420 server.
This change sets those attributes as nullable.
Change-Id: If34d96fab4249f466f63b3740d1ff5eb68012462
(cherry picked from commit 1488d904e2ad19e1b6455f66e23cdb03243f6912)
b4a6f0fc19