graph/db: let ForEachNode take a context

autopilot/interface.go

@@ -228,7 +228,7 @@ type GraphSource interface {
 	// the callback returns an error, then the transaction is aborted and
 	// the iteration stops early. Any operations performed on the NodeTx
 	// passed to the call-back are executed under the same read transaction.
-	ForEachNode(func(graphdb.NodeRTx) error) error
+	ForEachNode(context.Context, func(graphdb.NodeRTx) error) error
 
 	// ForEachNodeCached is similar to ForEachNode, but it utilizes the
 	// channel graph cache if one is available. It is less consistent than