LU-12758 quota: clear default flag for new ID

When setting the quota limits as 0 by "lfs setquota", the default
flag won't be cleared if the lquota_entry is just created for some
quota ID at the first time because the quota limits are the same.

Change-Id: I7f44ce0cb13783ca5bede2f55cd0707f1ccbc8ca
Signed-off-by: Hongchao Zhang <hongchao@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/36236

Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Shilong Wang <wshilong@ddn.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>

lustre/quota/qmt_handler.c

@@ -191,15 +191,16 @@ quota_set:
 		dirtied = true;
 	}
 
-	if (dirtied) {
-		if (!is_default && lqe->lqe_is_default) {
-			LQUOTA_DEBUG(lqe, "the qid %llu has been set quota"
-				     " explicitly, clear the default flag",
-				     lqe->lqe_id.qid_uid);
+	if (!is_default && lqe->lqe_is_default) {
+		LQUOTA_DEBUG(lqe, "the qid %llu has been set quota"
+			     " explicitly, clear the default flag",
+			     lqe->lqe_id.qid_uid);
 
-			qmt_lqe_clear_default(lqe);
-		}
+		qmt_lqe_clear_default(lqe);
+		dirtied = true;
+	}
 
+	if (dirtied) {
 		if (!is_updated) {
 			/* write new quota settings to disk */
 			rc = qmt_glb_write(env, th, lqe, LQUOTA_BUMP_VER, &ver);