Bug 21467: Prevent tests to fail

Bug 21467: Prevent tests to fail

The following error is raised if TestBuilder generates too big numbers:
 Out of range value for column 'tax_value_on_ordering'

     UPDATE aqorders
     SET
         tax_value_on_ordering = quantity * ecost_tax_excluded * tax_rate_on_ordering,
         tax_value_on_receiving = quantity * unitprice_tax_excluded * tax_rate_on_receiving
     WHERE ordernumber = ?
 "] at /home/vagrant/kohaclone/C4/Acquisition.pm line 1484.

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>