修复内存统计BUG；添加全局初始化API；

cache/test_demo/tango_cache_test.c

@@ -310,6 +310,7 @@ int main(int crgc, char  **arg)
 	}  
 	init_fifo();
 	
+	tango_cache_global_init();
 	tango_instance = tango_cache_instance_new(ev_base, "./pangu_tg_cahce.conf", "TANGO_CACHE", runtime_log);
 
 	tv.tv_sec = 10;