Fix DepositReserveAsset fees payment (#3340)

The `fee` should be calculated with the reanchored asset, otherwise it
could lead to a failure where the set aside fee ends up not being
enough.

@acatangiu

---------

Co-authored-by: Adrian Catangiu <adrian@parity.io>

polkadot/node/test/service/src/chain_spec.rs

@@ -169,6 +169,7 @@ fn polkadot_testnet_genesis(
 				paras_availability_period: 4,
 				no_show_slots: 10,
 				minimum_validation_upgrade_delay: 5,
+				max_downward_message_size: 1024,
 				..Default::default()
 			},
 		}