[MERGE] [FIX] FormView: avoid multiple creations of the same line in o2m...

[MERGE] [FIX] FormView: avoid multiple creations of the same line in o2m fields when the save action fails (e.g. forgot one required field)

This is done by removing the added action 'prepend_on_create' that can be present as many time as we pressed the save button

lp bug: https://launchpad.net/bugs/1265705 fixed

bzr revid: mat@openerp.com-20140414081003-290q4v21q01m4rsi