OAIHarvest: conversion argument name upgrade 

* Adds the missing upgrade script for changes done to OAI harvest
  source arguments in f9271a0 that could cause name problems during
  harvesting when upgrading an existing installation.

* Amends the web-tests to look for the proper new name.

Signed-off-by: Jan Aage Lavik <jan.age.lavik@cern.ch>