simplify utility code

This proposal contains two commits.

1. The first commit fixes all PEP8 issues in the NetUtils module, making possible to use an automated syntax checking and lint, based on `flake8` (a widespread practice in Python-based RedHat projects)
2. The second proposal replaces IPRSocket with IPRoute, significantly simplifying the code — but its usage restricts the dependency to pyroute2 >= 0.3.2, so, probably, it has to wait pyroute2-0.3.2 in Fedora updates.