Merge steps/nm_mock.py and suspend.py
Possible followup to !1481 (merged).
Adding a mocker correctly is a bit tricky. It seems to me that it could be alleviated by merging them to a single step file with few common functions:
- one to handle:
- cleanup set up
- actual mocker start
- wait until the mocker appears on the bus
- other to check if the expected mocker is active or not within other steps