Keyword UNIFOUT causes file problems when running flow from Python

[lisajulia]

With this keyword, the SPE1CASE1.UNRST file could not be read in correctly at some point, until I've added a check in opm-models that checks this, this went unnoticed probably.

I've removed the keyword here: https://github.com/OPM/opm-simulators/pull/5474 The check in opm-models is implemented here: https://github.com/OPM/opm-models/pull/909 and used in opm-simulators here: https://github.com/OPM/opm-simulators/pull/5478