Added some more test cases for testing IPMI SEL.
Added some more test cases for testing IPMI SEL.

Test cases added:
    - Verify IPMI SEL Delete
    - Verify Empty SEL
    - Delete Non Existing SEL Entry
    - Delete Invalid SEL Entry

Resolves openbmc/openbmc-test-automation#515

Change-Id: Ia3cdb6dbb6c1dd582525356df5244c1981ede975
Signed-off-by: Rahul Maheshwari <a806e6fd77e56dd64ff6084a06bbf3a5a70392ef@in.ibm.com>

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