Avoid the double-free (first in fts_read, second in fts_close) that

would occur when an `active' directory is made inaccessible (e.g.,
via chmod a-x) during a traversal.

(fts_read): After a failed fchdir, update sp->fts_cur
before returning.  Reproduce this failure by
mkdir -p a/b; cd a; chmod a-x . b
Reported by Stavros Passas.

lib/fts.c

@@ -522,6 +522,7 @@ next:	tmp = p;
 		if (p->fts_level == FTS_ROOTLEVEL) {
 			if (FCHDIR(sp, sp->fts_rfd)) {
 				SET(FTS_STOP);
+				sp->fts_cur = p;
 				return (NULL);
 			}
 			fts_load(sp, p);