Fix direct calls behavior.

 - Bug 1034068 — Trying to call a non-registered identity
 - Bug 1034537 — Trying to call an array of identities is not working as expected
I know this isn't implemented into this specific PR, but I wonder if it's safe to rely on the "host" information from the request here (versus a conf parameter).

Also, if the (Amazon) load balancer isn't handling websockets properly, we could do the round robin here.