fts: Stop abusing the comma operator.

MFC after:	1 week
Sponsored by:	Klara, Inc.
Reviewed by:	allanjude
Differential Revision:	https://reviews.freebsd.org/D49624

(cherry picked from commit 5abef29)

Author: dag-erling

lib/libc/gen/fts.c

@@ -901,10 +901,12 @@ fts_stat(FTS *sp, FTSENT *p, int follow, int dfd)
 	int saved_errno;
 	const char *path;
 
-	if (dfd == -1)
-		path = p->fts_accpath, dfd = AT_FDCWD;
-	else
+	if (dfd == -1) {
+		path = p->fts_accpath;
+		dfd = AT_FDCWD;
+	} else {
 		path = p->fts_name;
+	}
 
 	/* If user needs stat info, stat buffer already allocated. */
 	sbp = ISSET(FTS_NOSTAT) ? &sb : p->fts_statp;