SchemaRouter cannot route to services running in the same instance of MaxScale

My situation is that I've got a number of Master-Slave pairs that I would like to balance with `readconnroute` and then aggregate all of those within a `schemarouter` so as to present a single service entry point to my environment.

However, while `readconnroute` and `schemarouter` work individually I get the following error when using them in tandem:

error : [main-schemarouter] Failed to connect to server 'rtr-foo' (127.0.0.1:33001) when checking authentication user credentials and permissions: 2013 Lost connection to MySQL server at 'handshake: waiting for inital communication packet', system error: 110

I've done some basic verification that the service is running on :33001 and accepts connections via the mysql CLI.

I was advised by markusjm on IRC [#maria@freenode] to file this as a bug.

I've attached the relevant config and the full log of the invocation.