markers/skipper.py may have a problem

[mfalesni]

I was investigating the error with differing test collections on upstream. I figured out the only tests that make troubles are those marked with long_running and perf - these are handled by the skipper module.

If you run a parallel sprout session without any filtering params, there will be a lot of differences, like slaves have long_running tests collected and master does not. So adding --long-running to the invocation reduces the collection difference only to the perf tests.

I dumped the conf.slave_config and it seems the conf.slave_config.options.long_running is set correctly ...

@psav @RonnyPfannschmidt @jkrocil