_add_persona_from_contact: always return the persona
_add_persona_from_contact: always return the persona

In some case we may be interested by using the persona even if it was already
existing.

https://bugzilla.gnome.org/show_bug.cgi?id=671714

GNOME/folks,pwithnall/folks,pwithnall/folks,renatofilho/folks2,renatofilho/folks2,renatofilho/folks,renatofilho/folks,renatofilho/folks2,renatofilho/folks,pwithnall/folks,GNOME/folks,GNOME/folks,renatofilho/folks2,renatofilho/folks