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_data.sql

@@ -28,7 +28,6 @@ SELECT LOWER( REPLACE((SELECT REPLACE(@@hostname,'_','\_')),'%','\%') )INTO @cur
 SELECT '{"access":18446744073709551615}' INTO @all_privileges;
 SELECT '{"access":18446744073709551615,"plugin":"mysql_native_password","authentication_string":"invalid","auth_or":[{},{"plugin":"unix_socket"}]}' into @all_with_auth;
 
-
 -- Fill "global_priv" table with default users allowing root access
 -- from local machine if "global_priv" table didn't exist before
 CREATE TEMPORARY TABLE tmp_user_nopasswd LIKE global_priv;