filter_struct(): Add support for invert arg
filter_struct(): Add support for invert arg

Added support for invert argument to filter_struct() function:

- invert: Invert the results.  Instead of including only matching entries in
  the results, include only NON-matching entries in the results.

Change-Id: If1e854f5f360384965917fde40f0036cfb22eba7
Signed-off-by: Michael Walsh <10404802c7de463f402c4a18638106ca1b12ef61@us.ibm.com>

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