[xfrout2] Merge branch 'master' into xfrout2
[xfrout2] extended MockSocketSessionForwarder for mocking close() further.

it now honors disableClose() correctly.  it also supports new enableClose(),
canceling the disable.  these extensions will be needed for auth tests later.
[xfrout2] use SocketSessionForwarder for xfrout.

most of the changes should be trivial interface adjustments.
[xfrout2] make sure AuthSrv is destroyed before exiting from main().

otherwise there could be a kind of duplicate close() for the unix domain
sockets used in SocketSessionForwarders.  this was already an issue with ddns,
and xfrout has the same issue.  This change should fix it for both.
[xfrout2] enabled new version of XfroutServer that uses SocketSessionReceiver.

now that bundy-auth has changed to use it.  Much of the now-unused code of
the older version remains to keep the diff small for now.  Cleanups changes
will follow.
[master] Merge branch 'xfrout2'