LP#1338731: support clients that send 99 then 93 when starting a raw connection

LP#1338731: support clients that send 99 then 93 when starting a raw connection

This patch adds the option, for raw transports, to allow clients
to send the SC Status (99) message first, then the Login (93)
message. It's arguable whether such behavior is standard or not,
but at least one SIP2 client (Relais), inflexibly requires such
behavior.

This option is enabled using the service-level attribute
"allow_sc_status_then_login".

Signed-off-by: Galen Charlton <gmc@esilibrary.com>