Add a test for stats["percentage_memory"]. ref: 0d961654821bc7295bfe9f8d43ab362569e73fc7
Add a test for stats["percentage_memory"]. ref: 0d961654821bc7295bfe9f8d43ab362569e73fc7

ariarijp/mackerel-agent-plugins,xorphitus/mackerel-agent-plugins,y-kuno/mackerel-agent-plugins,mackerelio/mackerel-agent-plugins,hiroakis/mackerel-agent-plugins,ki38sato/mackerel-agent-plugins,ki38sato/mackerel-agent-plugins,mackerelio/mackerel-agent-plugins,ariarijp/mackerel-agent-plugins,ki38sato/mackerel-agent-plugins,y-kuno/mackerel-agent-plugins,hiroakis/mackerel-agent-plugins,y-kuno/mackerel-agent-plugins,xorphitus/mackerel-agent-plugins,xorphitus/mackerel-agent-plugins,ariarijp/mackerel-agent-plugins,mackerelio/mackerel-agent-plugins,ariarijp/mackerel-agent-plugins,hiroakis/mackerel-agent-plugins,hiroakis/mackerel-agent-plugins,ki38sato/mackerel-agent-plugins,mackerelio/mackerel-agent-plugins,xorphitus/mackerel-agent-plugins,y-kuno/mackerel-agent-plugins