preload_basic_commands test fails when executed from root

[marcinslusarz]

It takes write permission from a file and expects overwriting it should fail.

[GBuella]

Those tests should not be run as root.

[marcinslusarz]

I agree. We just need to detect it and refuse to run tests at all (I think it's preferred) or skip some of them.

[GBuella]

Yup, libpmemfile should just abort when root.

[marcinslusarz]

libpmemfile tests, not libpmemfile!

[GBuella]

Well, both, that is the best.

[marcinslusarz]

Then we wouldn't be able to test libpmemfile with pjdfstest. And I don't see any problem with handling root correctly. We already support chown, capabilities affecting file APIs, setuid & co.