Correct an issue when stats use old stats (example network). Had also to deal with the export CSV module not working.

Issue #1514 already corrected by issue #1348. Nevertheless, this commit improve code quality off the network plugin

Hey, I'm just trying to be consistent.

Issue #1055 has been fixed in psutil 5.3.0 (see giampaolo/psutil#1074).

- wrong continued indentation
- missing whitespace after ':'
- unused imports
- expected 2 blank lines after class or function definition

Workarround for the issue931. Not solve the issue but implement correctly the --disable-<plugin> option for all plugins