valid_list support invalid_values/required_values
valid_list support invalid_values/required_values

Added support to valid_list function for 2 new arguments:

- invalid_values
- required_values

Also, corrected a few small errors.

Change-Id: Iec161b32ab2fce30cd42aa77168a9814dc099ed0
Signed-off-by: Michael Walsh <10404802c7de463f402c4a18638106ca1b12ef61@us.ibm.com>

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