Fix adding an existing batch sellable item to a workorder

Synchronize the batch item's stock before running the batch selection dialog
and don't send any item to be validated so the dialog can do the right thing.

By now it's the simplest thing to do, but we should solve the issue in a better
way in the future.

Fixes: http://bugs.async.com.br/show_bug.cgi?id=5510
Change-Id: I5797031e1f1e209526c35015b1fd1cb892ed64d9
Set focus chain got batch selection dialog

Change-Id: I5f7dcde025a7569b7295f91b8e44e1aa96b51b8a