More chown/chgrp dereferencing-related fixes.
* src/chown-core.c (change_file_owner): Don't use fts_statp if
we're dereferencing symlinks.
Reverse conjuncts, so that we use dereference file_stats
(aka ent->fts_statp) only *after* we've confirmed that
chopt->affect_symlink_referent is true. Otherwise, we might
use ent->fts_statp uninitialized.
Don't turn on FTS_NOSTAT when dereferencing symlinks.
* tests/chown/deref: Update the expected diagnostic, now that
this test case (trying to use "chown --dereference ..." on a
dangling symlink) takes a different code path.