BIND 10 #1820: remove DNSService::addServer()

[BIND 10 Development]

#1820: remove DNSService::addServer()
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                   Reporter:         |                 Owner:  jinmei
  jinmei                             |                Status:  accepted
                       Type:         |             Milestone:
  defect                             |  Sprint-20120403
                   Priority:         |            Resolution:
  medium                             |             Sensitive:  0
                  Component:         |           Sub-Project:  DNS
  Unclassified                       |  Estimated Difficulty:  0
                   Keywords:         |           Total Hours:  0
            Defect Severity:  N/A    |
Feature Depending on Ticket:         |
        Add Hours to Ticket:  0      |
                  Internal?:  0      |
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Comment (by jinmei):

 trac1820 is ready for review.

 There was actually one other place that used the mostly-unused
 interfaces of DNSService.  But it was only in unit tests, so I thought
 it still makes sense to clean it up and keep the public code simpler.

 While doing the cleanup I noticed many unsafe places in
 recursive_query_unittest (in terms of resource leak with exceptions),
 so I also made them safer.  This part is irrelevant to the subject of
 this task, but the branch is small so I think it's acceptable.

 While this branch modifies a publicly visible API, I don't think it
 worth a changelog entry because it's mostly for internal-only part of
 the API.

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Ticket URL: <http://bind10.isc.org/ticket/1820#comment:2>
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