[master] cleanup: removed dead code.

I suspect it was a leftover of an intermediate attempt that ended up with
    found = RdataSet::find(node->getData(), type);
at commi 32f6a873.

Whatever the intent was, it's clear the code does nothing, so cleaning it
up shouldn't harm anyway.

okayed on jabber.

src/lib/datasrc/memory/zone_finder.cc

@@ -561,10 +561,6 @@ InMemoryZoneFinder::find_internal(const isc::dns::Name& name,
                                  wild, &name));
     }
 
-    const RdataSet* currds = node->getData();
-    while (currds != NULL) {
-        currds = currds->getNext();
-    }
     found = RdataSet::find(node->getData(), type);
     if (found != NULL) {
         // Good, it is here