JChannelFactory addSingletonName handling broken

The expected path for the AS JChannelFactory's addSingletonName logic is broken – it thinks it is mutating the passed in config but it isn't.

Luckily this is minor because there's separate logic that executes when JGroups throws an UnsupportedOperationException – said logic works correctly and JGroups always throws the exception. But if a later release of JGroups fixed the UOE, this bug would be exposed.