avoid multiple patching of came_from in login overlay. fixes https://www.pivotaltracker.com/story/show/22154521
avoid multiple patching of came_from in login overlay.
fixes https://www.pivotaltracker.com/story/show/22154521

phihag/adhocracy,alkadis/vcv,SysTheron/adhocracy,DanielNeugebauer/adhocracy,phihag/adhocracy,SysTheron/adhocracy,liqd/adhocracy,liqd/adhocracy,DanielNeugebauer/adhocracy,phihag/adhocracy,alkadis/vcv,SysTheron/adhocracy,liqd/adhocracy,phihag/adhocracy,DanielNeugebauer/adhocracy,phihag/adhocracy,alkadis/vcv,DanielNeugebauer/adhocracy,DanielNeugebauer/adhocracy,alkadis/vcv,liqd/adhocracy,alkadis/vcv