[#48] Use more extra fee at container registration

Large inner ring requires more gas to make container registration.
Container contract makes balance transfers for each inner ring node
and it require extra gas to execute. This estimation should be enough
for seven inner ring nodes.

Later there should be heuristic evaluations for this: #47

Signed-off-by: Alex Vanin <alexey@nspcc.ru>

pkg/innerring/invoke/container.go

@@ -32,7 +32,7 @@ func RegisterContainer(cli *client.Client, con util.Uint160, p *ContainerParams)
 		return client.ErrNilClient
 	}
 
-	return cli.Invoke(con, extraFee, putContainerMethod,
+	return cli.Invoke(con, 2*extraFee, putContainerMethod,
 		p.Container,
 		p.Signature,
 		p.Key.Bytes(),