Redmine #4809: Fix several filestat() fields on Windows.

Some are best-effort, like permoct will always be 666 or 444, because
the only non-ACL file attribute on Windows that maps to Unix is the
read-only attribute.
Skip several tests that use inode data on Windows.
Fix several acceptance tests after the introduction of $(G.etc_group).

The main problem is that the path contains redundant '../../' parts
and the test doesn't expect that.

Redmine #4809.
Merge pull request #1577 from kacfengine/filestat_windows_fixes

Redmine #4809: Filestat windows fixes + test fixes