net-mgmt/py-ciscoconfparse: Update to 1.9.16

• Switch to PEP517 build framework.

• Convert to USE_PYTHON=pytest to simplify Makefile.

• Remove no longer required patch for newer releases of setuptools.

Changelog since 1.5.51:

https://github.com/mpenning/ciscoconfparse/compare/v1.5.51...1.9.16