BIND 10 #2614: update b10-loadzone using generic DB creation

[BIND 10 Development]

#2614: update b10-loadzone using generic DB creation
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                   Reporter:         |                 Owner:
  jinmei                             |                Status:  new
                       Type:  task   |             Milestone:  New Tasks
                   Priority:         |              Keywords:
  medium                             |             Sensitive:  0
                  Component:         |           Sub-Project:  DNS
  loadzone                           |  Estimated Difficulty:  0
               CVSS Scoring:         |           Total Hours:  0
            Defect Severity:  N/A    |
Feature Depending on Ticket:         |
  loadzone-ng                        |
        Add Hours to Ticket:  0      |
                  Internal?:  0      |
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 When b10-loadzone tries to load a zone to a data source but the data
 source is not even yet initialized (which means, in the current
 implementation, there is no SQLite3 DB file), it relies on
 `DataSourceClient` internally performs this initialization.

 But such initialization should actually be removed from
 `DataSourceClient` (it's provided for compatibility, but was not
 intended to be a part of its responsibility), and its support is
 actually incomplete (see discussions in #2610).

 The right solution is to complete #1861, and have b10-loadzone use the
 generic data source initialization module.

 Maybe we shouldn't make it automatic though, and rather implement it
 as an option to b10-loadzone.

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Ticket URL: <http://bind10.isc.org/ticket/2614>
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BIND 10 Development