BIND 10 #2235: (simplified) support "load zone" command in the configurator thread

[BIND 10 Development]

#2235: (simplified) support "load zone" command in the configurator thread
-------------------------------------+-------------------------------------
            Reporter:  jinmei        |                        Owner:
                Type:  task          |                       Status:  new
            Priority:  medium        |                    Milestone:  Next-
           Component:  data source   |  Sprint-Proposed
           Sensitive:  0             |                     Keywords:
         Sub-Project:  DNS           |              Defect Severity:  N/A
Estimated Difficulty:  0             |  Feature Depending on Ticket:
         Total Hours:  0             |  background zone loading
                                     |          Add Hours to Ticket:  0
                                     |                    Internal?:  0
-------------------------------------+-------------------------------------
 A subtask of #2201, depend on #2234.

 This is a simplified version of #2212, reducing dependencies.

 This task extends the newly introduced "data source configurator"
 thread (#2205) to support background zone reloading.

 It will be based on the current content of LoadZoneCommand::exec(),
 but works as follows:

 - first call `ConfigurableClientList::reloadCache()` introduced in #2234
 - then acquire the lock introduced in #2202
 - then call `ConfigurableClientList->reinstallCache()`
 - then release the lock
 - then call `ConfigurableClientList->cleanupCache()`

 Note that updater reloadCache() can throw.

-- 
Ticket URL: <http://bind10.isc.org/ticket/2235>
BIND 10 Development <http://bind10.isc.org>
BIND 10 Development