Test system LEDs.

This change includes:
   - Added test cases to turn on/off heartbeat, beep and
     identify LEDs.
   - Added keywords to get and set physical LED state.
   - Skipped these test case for Witherspoon system.

Resolves openbmc/openbmc-test-automation#404

Change-Id: I64c939d50852e4b627ad8bf559b75da4f95237a1
Signed-off-by: Rahul Maheshwari <rahulmaheshwari@in.ibm.com>
3 files changed