Drivers of Redfish emulator now cache the
outcome of a select calls choosing either the
two policies:
* Cache the information for the lifetime of the
emulator process if it's unlikely for such
data to get out of sync
* Cache the more dynamic information just for
the duration of a single Redfish REST API
call
This change improves emulator responsiveness.
Change-Id: Ief46a0a7b82900ccf6d4c9ebb417f711a9b00513
b13ea4e9c7