fix: wire up proper linksystem to traverser (#411)

Was missed in #356

This doesn't break anything obvious because the loader isn't used from the
traverser's linksystem, and the traverser sets up defaults where the provided
linksystem is missing them. But, we don't get certain things, like
KnownReifiers, which are kind of important.

requestmanager/server.go

@@ -157,7 +157,7 @@ func (rm *RequestManager) requestTask(requestID graphsync.RequestID) executor.Re
 				return nil
 			},
 			Chooser:       ipr.nodeStyleChooser,
-			LinkSystem:    rm.linkSystem,
+			LinkSystem:    *ipr.lsys,
 			Budget:        budget,
 			PanicCallback: rm.panicCallback,
 		}.Start(ctx)