rpcserver: add breathing room to AddInvoice quote max amt

Author: GeorgeTsagk

rpcserver.go

@@ -7730,6 +7730,14 @@ func (r *rpcServer) AddInvoice(ctx context.Context,
 		maxUnits = assetUnits.ToUint64()
 	}
 
+	// Since we used a different oracle price query above calculate the max
+	// amount of units, we want to add some breathing room to account for
+	// price fluctuations caused by the small time delay, plus the fact that
+	// the agreed upon quote may be different. If we don't add this safety
+	// window the peer may allow a routable amount that evaluates to less
+	// than what we ask for.
+	maxUnits = (maxUnits * 105) / 100
+
 	resp, err := r.AddAssetBuyOrder(ctx, &rfqrpc.AddAssetBuyOrderRequest{
 		AssetSpecifier: &rfqrpc.AssetSpecifier{
 			Id: &rfqrpc.AssetSpecifier_AssetId{