Increase code quality and reduce McCabe complexity by improving maintenance

[cmagnobarbosa]

Today the topology NApp has a code quality below 7 (Scrutinizer 6.8) and some methods have McCabe complexity above 10, to improve maintenance it is necessary to change this.

McCabe's complexity above 8 (obtained using https://github.com/PyCQA/mccabe):

144:4: 'Main._restore_switch' 13
339:4: 'Main.enable_interface' 9
369:4: 'Main.disable_interface' 9
834:4: 'Main.update_instance_metadata' 8

Suggested changes:

• Increase code quality to over 7.
• Reduce McCabe complexity to below 10.
  • Refactor the _restore_switch method

References:

• https://www.aivosto.com/project/help/pm-complexity.html
• https://blog.codecentric.de/en/2011/10/why-good-metrics-values-do-not-equal-good-quality/
• https://dzone.com/articles/what-exactly-is-mccabe-cyclomatic-complexity
• https://github.com/PyCQA/mccabe