dbus-sdr: Make GetSDR more robust against dbus failure.

SDR list should be persistent while occasional SDR reading error due
to underlayer dbus failure. The improvement consists of the following
aspects:
  1. SDR type is merely determined by sensorTree(from ObjectMapper),
  whose mechanism is the same as SDR index.
  2. Alway return next sdr id even when failure.
  3. Avoid unnecessary dbus call when IPMI host doesn't requires the SDR
  body.

Signed-off-by: Hao Jiang <jianghao@google.com>
Change-Id: If7d7bbb6db587c727f6ea5bcb7a7984f1ed47a80
Signed-off-by: Willy Tu <wltu@google.com>
2 files changed