Cleanup: Don't use DataHelper.writeLong() for a single byte

core/java/src/net/i2p/data/i2cp/AbuseSeverity.java

core/java/src/net/i2p/data/i2cp/I2CPMessageImpl.java

core/java/src/net/i2p/data/i2cp/MessagePayloadMessage.java

core/java/src/net/i2p/data/i2cp/MessageStatusMessage.java

...ava/src/net/i2p/data/i2cp/ReceiveMessageBeginMessage.java

...java/src/net/i2p/data/i2cp/SendMessageExpiresMessage.java

core/java/src/net/i2p/data/i2cp/SendMessageMessage.java

router/java/src/net/i2p/data/i2np/DeliveryInstructions.java

router/java/src/net/i2p/data/router/RouterAddress.java

...java/src/net/i2p/router/message/GarlicMessageBuilder.java