ignore verisign lowbalance-poll resData nodes

EPP-RTK has no concept of how to deal with these, and chokes on poll
messages that contain these nodes.  Just ignore them.
parseGenericResult: add missing xmlns:xsi if needed

This ensures that extension strings contain the xmlns:xsi attribute so
that extension strings can be parsed with a namespace-aware parser
as-is, as standalone XML documents, even if xmlns:xsi was not set on
each extension string by the server