Remove obsolete/deprecated thing

[marxsk]

For next major version we can remove obsolete/deprecated thing. This issue should track pieces that we should take look at and remove:

• Support for --plug [switch]:[plug] notation that was used before (e.g. in fence_apc)
• Support for enable/disable instead of standard on/off (in fencing.py)

Currently, there is not enough of the code to remove :)