Fix errorlog test cases

Fixes:
   - Sorting URL list
   - Replace hard-coded entry index to list indexing
   - With the new FW elog design change, the error log is now
     persistent on BMC reset or restarting the logging service
   - Add keyword to check if errorlog exist

Resolves openbmc/openbmc-test-automation#732

Change-Id: Iafe54824dc0ed4ef88acd8dd327cbc873cd740aa
Signed-off-by: George Keishing <gkeishin@in.ibm.com>
2 files changed