features/environment.py: log events, collect together them with NM log
As trace-level NM logs can get huge, it's sometimes handy to be able to get quickly to a given time, or to see at what stage of the scenario did something happened.
This change achieves that by addition of logging at various stages of behave scenario and then by collecting these messages together with the messages of NetworkManager.service unit.
Edited by David Jaša