Add test for BIOS Post codes
Add test for BIOS Post codes

Changes:
     - Added test cases for Host reboot and host poweroff

Tested:
     Ran successfully redfish/systems/LogServices/test_post_codes.robot

Change-Id: Icff9eb93225ea0de5113adff14a439cafade8c7a
Signed-off-by: George Keishing <bef0a9ecac45fb57611777c8270153994e13fd2e@in.ibm.com>

openbmc/openbmc-test-automation,openbmc/openbmc-test-automation