_apply_linux_xattr_rec(): do nothing if no rec; fix restricted access test.

_apply_linux_xattr_rec(): do nothing if no rec; fix restricted access test.

If the metadata object has no linux_xattr, don't do anything at all in
_apply_linux_xattr_rec(), and don't test the filesystem for xattr
support to determine whether or not to expect an xattr error, because
EACCES trumps the other errors.

This should be more efficient and fix a
test_apply_to_path_restricted_access() failure.

Thanks to Sebastian Schumb <sebastian@sebastians-site.de> for
reporting the problem and helping track down the fix.

Signed-off-by: Rob Browning <rlb@defaultvalue.org>