routing+lnrpc: move default payment timeout out of router

This commit moves the default timeout out of router and thereby fixes a
bug that caused SendToRoute to not return the actual error, but a
timeout result instead. SendToRoute only tries a single route, so a
timeout should never happen.

rpcserver.go

@@ -3070,6 +3070,7 @@ func (r *rpcServer) dispatchPaymentIntent(
 			RouteHints:        payIntent.routeHints,
 			OutgoingChannelID: payIntent.outgoingChannelID,
 			PaymentRequest:    payIntent.payReq,
+			PayAttemptTimeout: routing.DefaultPayAttemptTimeout,
 		}
 
 		preImage, route, routerErr = r.server.chanRouter.SendPayment(