Use all staging archs in adi projects

This replaces #1304 with a more brute force approach to fix not only
32bit libs but all failures we see on i586. We waste so much energy
retrying failed builds, it's really not worth it not trying i586 on
adi.

osclib/stagingapi.py

@@ -1431,12 +1431,16 @@ class StagingAPI(object):
           {repository}
             <path project="{self.cstaging}" repository="standard"/>
             <path project="{self.project}" repository="standard"/>
-            <arch>x86_64</arch>
           </repository>
           {images_repo}
           {containerfile_repo}
         </project>"""
 
+        root = ET.fromstring(meta)
+        repository = root.find('.//repository[@name="standard"]')
+        for arch in self.cstaging_archs:
+            a = ET.SubElement(repository, 'arch')
+            a.text = arch
         url = make_meta_url('prj', name, self.apiurl)
         http_PUT(url, data=meta)
         # put twice because on first put, the API adds useless maintainer