Buying shares of the right growth stocks can help set you up for a happy retirement. Sometimes you get the chance to buy shares at discounts, which can be to your advantage. Here are two growth stocks that have stumbled but are still on track to deliver excellent returns for long-term investors.1. AlibabaShares of Alibaba (BABA -0.73%) have surged year to date but are still down 58% from their previous highs. A slow economic recovery and increasing competition in China's e-commerce market have weighed on th ...