fix bugs

[IwakuraRein]

• call m_pRender[m_rndMethod]->destroy() before m_pRender[m_rndMethod]->create(). Otherwise, the previous pipeline and pipeline layout won't be destroyed when a scene is loaded.

• add if (m_busy) return; to SampleExample::onKeyboard(). Otherwise, when user is pressing the keyboard while loading the scene, some unpredictable multithread bugs may happen.

Signed-off-by: Alex alexfu@seas.upenn.edu

[IwakuraRein]

Still got this sign off issue. I will try again in the new pr.