sensor-cache: Add cache for sdr and threshold

Add cache for sdr and threshold so that it does not have to make DBus
calls every time.

Tested: Verify the ipmi sensor list/sdr list works fine.

Signed-off-by: Lei YU <yulei.sh@bytedance.com>
Change-Id: I8047144b1f66b95414905d1a065c9bf54410f0f5
1 file changed