Check extended attributes supported status also when setting them.

This should not be necessary, since we already checked when getting
them. However, fakeroot seems to return this occasionally when running
tests, so better to check both times.

Addition to issue 2545.
Remove redundant SELinux code.

This is covered in the CopyFilePermissionsDisk() function, and should
have been part of commit a3f1a964ad5e079f8a.

Addition to issue 2545.
Merge pull request #699 from kacfengine/fakerootFix

Fakeroot fix