XML Datastream Settings page: Adjust arguments

As you know, the path to the "XML Datastream Settings" page changed from: <ul><li>"/admin/islandora/sync/xml-datastreams" (7.x-1.3) to</li> <li>"/admin/islandora<strong>/tools/</strong>sync/xml-datastreams" (7.x-1.4, HEAD).</li></ul>

In the Islandora Sync module, hook_menu() grabs arguments from the URL -- such as the datastream ID. However, the indexes of these arguments were not adjusted after the path changed. As a result, instead of grabbing, say, "MODS" from the URL, it grabs the preceding argument "xml-datastreams" instead. The subsequent functions are fed a bad datastream ID, making it impossible to edit or delete any existing XML datastream settings. This patch adjusts the arguments to fix this problem.
 
<em>NOTE:</em> Clear Drupal's performance cache after applying this patch.