osclib/core: package_kind(): require releasename to differ from package for maintenance_update.

When releasename does not differ it is essentially the same as no
releasename at all, but since OBS allows this and some source packages
contain such a value need to make check more specific.

See #2294 for an example.

osclib/core.py

@@ -550,7 +550,7 @@ def package_kind(apiurl, project, package):
 
         raise e
 
-    if root.find('releasename') is not None:
+    if root.find('releasename') is not None and root.find('releasename').text != package:
         return 'maintenance_update'
 
     # Some multispec subpackages do not have bcntsynctag, so check link.