Return valid XML document in reply.getContain()

[isartcanyameres]

When the content of a response has multiple XML elements, resulting reply.getContain() is not a valid XML document because it has multiple top-level elements.
This behaviour may appear in several queries. I.e. interface-information, software-information, etc.

It may require a test suite and some fixes in TransportContentParser class to avoid having multiple top-level elements independently of the message content.

A possible solution would be to apply broad in the class the solution applied in software-information. That is, appending the top-level element containing the query type (i.e. "software-information")