--benchmark-disable still saves json files

[TauPan]

Hi, I just upgraded from 3.2.3 to 3.4.1 (more or less by accident) and noticed that benchmark now saves json files if --benchmark-disable is given together with --benchmark-autosave

(I use these flags in pytest.ini so I can just give --benchmark-enable and don't need to give autosave as well. Maybe I should not do that, I don't know.)

I think the previous behaviour was to issue a warning.

There are a couple of problems I see with this:

1.) I get separate json files for each process I run with pytest-xdist
2.) Those json files contain no actual benchmark information
3.) This throws pytest-watch run with e.g. --spool 1000 -- --testmon --testmon-forceselect which will interrupt itself every time the json dump is written. (Of course --ignore=.benchmarks helps against that.)
4.) Those json files clutter the checkout.

My personal opinion is that saving benchmark data makes no sense if no actual benchmarks were run, so I'm happier with the warning in that case.

Any opinion or advice is appreciated here. I'm considering either downgrading, or changing the flags in pytest.ini, since I do rarely run benchmarks. The --ignore flag for pytest only helps against problem number 3.

[TauPan]

Looking at the code this looks like an oversight to me, so I created a PR.