Fixed some errors & warnings when running mariadb-upgrade on MySQL instance

- Moved view checks after privilege tables are fixed. This is to avoid
  warnings about wrongly defined mysql.proc when checking views.
- Don't use stat tables before they have been fixed.
- Don't run mysql_fix_view() if 'FOR MYSQL' is used if the view is
  already a MariaDB view.
- Added 'FOR UPGRADE' as an option for 'REPAIR VIEW' to be able to
  detect if the REPAIR command comes from mariadb_upgrade. In this
  case we get a warning, instead of an error, if a definer of a view
  does not exists.

scripts/mysql_system_tables.sql

@@ -46,7 +46,6 @@ INSERT INTO tmp_user_sys (Host,User,Priv) VALUES ('localhost','mariadb.sys','{"a
 INSERT IGNORE INTO global_priv SELECT * FROM tmp_user_sys WHERE 0 <> @need_sys_user_creation;
 DROP TABLE tmp_user_sys;
 
-
 CREATE DEFINER='mariadb.sys'@'localhost' SQL SECURITY DEFINER VIEW IF NOT EXISTS user AS SELECT
   Host,
   User,