修正linux下编译问题
witnessed_timeout_handler.cpp: In member function 'virtual void KBEngine::WitnessedTimeoutHandler::handleTimeout(KBEngine::TimerHandle, void*)':
witnessed_timeout_handler.cpp:58: warning: 3rd expression in for has no effect
witnessed_timeout_handler.cpp:80: error: no matching function for call to 'KBEngine::DebugHelper::debug_msg(boost::format)'
/root/kbengine-1/kbe/src/lib/helper/debug_helper.hpp:137: note: candidates are: void KBEngine::DebugHelper::debug_msg(boost::format&)
/root/kbengine-1/kbe/src/lib/helper/debug_helper.hpp:138: note:                 void KBEngine::DebugHelper::debug_msg(std::string)
witnessed_timeout_handler.cpp:56: warning: unused variable 'witness_timeout_dec'