BIND 10 #1764: make SyncUDPServer even more simpler (and probably faster)

[BIND 10 Development]

#1764: make SyncUDPServer even more simpler (and probably faster)
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                   Reporter:         |                 Owner:
  jinmei                             |                Status:  new
                       Type:  task   |             Milestone:  Next-Sprint-
                   Priority:  high   |  Proposed
                  Component:         |            Resolution:
  b10-auth                           |             Sensitive:  0
                   Keywords:         |           Sub-Project:  DNS
            Defect Severity:  N/A    |  Estimated Difficulty:  0
Feature Depending on Ticket:  auth   |           Total Hours:  0
  performance                        |
        Add Hours to Ticket:  0      |
                  Internal?:  0      |
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Comment (by vorner):

 While I agree with these simplifications, I'd like to say that the
 check_in callback is not used at all and the answer_callback could be
 removed from the resolver as well, so we could remove these hooks from
 interface completely. That would be generally cleaner.

 I needed to add one stopped check because the tests were failing without
 it. Maybe it is OK for the class to behave differently there, but I like
 it having the same interface.

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Ticket URL: <http://bind10.isc.org/ticket/1764#comment:1>
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