Remove a needless comment.

VirtualDataStore::stop() is public function.
Fix scope of constructor & desctructor of UnifiedDataStore
fixed the bug in which threads to get Zabbix data and Nagios data are not started.

This bug has been added in commit: 4e907f0c when the start() of
vdsZabbix and vdsNagios were replaced with unifiedDataStore
in mainRoutine(). The call of start() was missing.
Fix place of some functions
extended DBClientHatohol::getTriggerInfoList() only to get triggers of the specified server.