Issue #2803: fixed RenderTextureTest's memory leaking
Merge branch 'master' of https://github.com/cocos2d/cocos2d-js-tests into Iss2803_V2.1.6Release
Merge pull request #212 from dingpinglv/Iss2803_V2.1.6Release

Issue #2803: fixed RenderTextureTest's memory leaking