[PATCH v2] tests: gracefully handle AppArmor userns containment

[Florian Weimer]

* Maxim Kuvyrkov:

> Where is EACCES coming from?  I could not find documentation
> mentioning EACCES as a possible error condition for unshare().

Presumably a seccomp filter or a Linux security module.  We don't do
that error code translation in the main library (e.g., for clone3), but
it has crept into the test suite over time.

Thanks,
Florian