Also, let the new SwTextBoxHelper::restoreLinks() restore also the
RES_CNTNT of the *old* draw formats, not only the link between the new
draw and fly formats.

This allows properly preserving the link between draw and fly formats,
when they are in the header (and so copied in and out variously).

Change-Id: I101ff06533e2ea27abea8bed171ed69c9649ebe8