PR#449 Make sure to fix encoding all RPM Headers

Merges #449
https://pagure.io/koji/pull-request/449

hub/kojihub.py

@@ -9883,10 +9883,7 @@ class RootExports(object):
             raise koji.GenericError('either rpmID or taskID and filepath must be specified')
 
         headers = koji.get_header_fields(rpm_path, headers)
-        for key, value in headers.items():
-            if isinstance(value, six.string_types):
-                headers[key] = koji.fixEncoding(value, remove_nonprintable=True)
-        return headers
+        return koji.fixEncodingRecurse(headers, remove_nonprintable=True)
 
     queryRPMSigs = staticmethod(query_rpm_sigs)