Hedge funds and investors in exchange-traded notes are plowing money into bets that pay off should last week’s soothing of U.S. stock market turbulence prove temporary. With the Chicago Boards Options Exchange Volatility Index closing below 20 for just the third time this year, a pair of securities that track the gauge have seen combined inflows of $140 million over the last week after losing almost $1 billion to start 2016. Hedge...