Work orders that has sales can't have items changed

On optical plugin the work orders are created with a sale already associated
with it, so we can't allow changes on work orders after a sale.

Change-Id: I4d87e53ba291cec8651738692f6b3fc44fbc61bb
fixes: http://bugs.async.com.br/show_bug.cgi?id=5518
Merge "Work orders that has sales can't have items changed"