Point to config examples residing in vars

[htgoebel]

In the docs point to examples residing in vars, e.g.example_static.yml

Also fix variable names there:

(21:24:16) drybjed: ok, but did you change the ifupdown_default_interfaces to ifupdown_interfaces? it probably is misleading in the example files...

[ypid]

Might take a while until the docs reach https://docs.debops.org/en/latest/ due to debops/docs#241 but the issue is fixed in git master.