The cybersecurity specialist has underperformed the broad market recently, but there may be a turnaround on the horizon.Cybersecurity specialist Fortinet (FTNT -1.15%) hasn't been among the best performers on the stock market in the past three years with its 16% return lagging peers such as Palo Alto Networks and CrowdStrike Holdings by a wide margin. What's more, Fortinet stock has underperformed the S&P 500's 28% return over the same period.The situation hasn't improved this year, either, as the cybersecu ...