testsuite: Fixed several pylint 1.0 issues
POSIX: Fix verification of symlinks

* Stat the link itself, not its target
* Get SELinux context from the link, not the target
* Don't get ACLs at all; symlinks don't have their own ACLs

The first issue listed wasn't actually a bug, because none of the
information queried from the target by the stat call was actually used
in verification, but it's been fixed for completeness.