BIND 10 #1868: use SocketSessionReceiver for receiving xfr messages from b10-auth at xfrout

[BIND 10 Development]

#1868: use SocketSessionReceiver for receiving xfr messages from b10-auth at
xfrout
-------------------------------------+-------------------------------------
            Reporter:  jinmei        |                        Owner:
                Type:  task          |                       Status:  new
            Priority:  medium        |                    Milestone:  Next-
           Component:  xfrout        |  Sprint-Proposed
           Sensitive:  0             |                     Keywords:
         Sub-Project:  DNS           |              Defect Severity:  N/A
Estimated Difficulty:  0             |  Feature Depending on Ticket:
         Total Hours:  0             |          Add Hours to Ticket:  0
                                     |                    Internal?:  0
-------------------------------------+-------------------------------------
 This is the xfrout part of #1867 (and depends on it).

 With this change, we can also eliminate the hack of `_guess_remote()`
 because the `SocketSession` framework also forwards the source address
 information.

 We'll also update b10-auth to enable the code using
 `SocketSessionForwarder` for forwarding xfr messages.

-- 
Ticket URL: <http://bind10.isc.org/ticket/1868>
BIND 10 Development <http://bind10.isc.org>
BIND 10 Development