Update physical LEDs as part of Lamp test

- Add the getSubTreePaths method for utils and update all physical
  LEDs.

- Uses GetSubTreePath on Physical LED paths and interfaces and
  updates all the LEDs to ON as part of start or restart of the test.

- When the lamp test is stopped or the timer expires, all the LEDs
  are turned OFF.

Signed-off-by: George Liu <liuxiwei@inspur.com>
Change-Id: I27727db62fe963a1a7c8b391d73801bcaf9efeec
8 files changed