Power Error test use case fix

The code for settingsd being fixed by openbmc/openbmc#552.
The power cap attribute valid values validation is now
in force.

These changes address the following:
   - Fixes 2 use cases of tests for error scenario
   - Add Test case name tagging
   - Documentation
   - Add new Keyword with to return error msg for
     checking the message returned by settingsd
   - Alignment and minor code cleanup

Resolves openbmc/openbmc-test-automation#118

Change-Id: Ic253fb58d6f6efeddb4afa3d8c8c12ccf176ed1a
Signed-off-by: George Keishing <gkeishin@in.ibm.com>
1 file changed