fixup! Attr: changed semantics of (internal) move method

While it should not be the case, that the Attr's internal method free's
the passed attribute, as some of the other internal methods pass
non-allocated pointers to it, the methods visible by the user should
indeed free things, where the ownership of every inner element is
already transfered. This was adjusted now. As some tests have taken
advantage of the fact, that while not to be changed, the old pointers
were still accessible, they had to be adjusted.