Fix MySQL update procedure with incorrect handling of the FileIndex type

Fix MySQL update procedure with incorrect handling of the FileIndex type

Upgrade fails as follows:

   This script will update a Bacula MySQL database
   from any from version 12-15 or 1014-1021 to version 1022
   which is needed to convert from any Bacula Enterprise
   version 4.0.x or later to version 12.4.x
   or Bacula Community versions 5.0.x, 5.2.x, 7.4.x, 9.x.x to
   Community version 11.0

   Depending on the current version of your catalog, you may
   have to run this script multiple times

   ERROR 1264 (22003) at line 24: Out of range value for column 'FileIndex' at row 1
   Update of Bacula MySQL tables from 16 to 1017 failed.

This would indicate that the file_temp table is using an unsigned
version of FileIndex however it should be signed, so changing the
schema of that temp table makes it go further,